PDF Page Sizes Explained: A4, Letter, Legal, and Custom

Page size affects printing, viewing, and document portability. Understanding standard sizes, regional preferences, and conversion considerations ensures your PDFs work correctly across different contexts and geographies.

Why Page Size Matters

Page size is more than a technical detail—it affects how people interact with your documents. Incorrect page size causes printing problems with content cut off or oddly positioned. Documents designed for one size look wrong when printed on different paper. International collaboration faces challenges when North American Letter meets European A4. Digital viewing experiences vary based on page proportions and screen orientation. Archival and compliance requirements may mandate specific page sizes. Understanding page sizes prevents these problems and ensures documents work properly in all intended contexts.

Standard Page Sizes

Letter (8.5 × 11 inches)

Letter size is the standard in the United States, Canada, Mexico, and parts of Latin America. It measures 8.5 inches wide by 11 inches tall (215.9 × 279.4 mm). Letter size originated from American paper manufacturing traditions and became the de facto standard through widespread use. Most U.S. printers default to Letter, office copy machines are designed for it, and filing cabinets and folders are sized accordingly. The slightly wider and shorter proportion compared to A4 affects page layout—documents designed for Letter often need adjustment for A4 printing and vice versa.

Related tools: Rotate Pages, Reorder Pages, Add Page Numbers, Merge PDF

A4 (210 × 297 mm)

A4 is the international standard used throughout Europe, Asia, Australia, Africa, and most of the world outside North America. It measures 210 millimeters wide by 297 millimeters tall (8.27 × 11.69 inches). A4 is part of the ISO 216 standard, which defines a consistent series of paper sizes based on mathematical ratios. The A-series uses an aspect ratio of 1:√2, meaning when you fold an A4 sheet in half, you get two A5 sheets with the same proportions. This mathematical elegance enables efficient paper use and scalability. A4 is slightly narrower and taller than Letter, which affects margin settings and text flow.

Legal (8.5 × 14 inches)

Legal size, primarily used in the United States, measures 8.5 inches wide by 14 inches tall (215.9 × 355.6 mm). The extra length compared to Letter provides more space for lengthy contracts, legal documents, and forms requiring extensive information on single pages. Legal size is common in law firms, courts, and government agencies but less prevalent in general business use. Many consumer printers don't support Legal size well, and international use is virtually nonexistent. Use Legal when document recipients expect it (legal or government contexts) but consider Letter or A4 for broader compatibility.

Tabloid/Ledger (11 × 17 inches)

Tabloid (portrait orientation) or Ledger (landscape orientation) is twice the size of Letter at 11 × 17 inches (279.4 × 431.8 mm). This larger format suits presentations, posters, diagrams, spreadsheets, and architectural drawings requiring more space than standard pages. Tabloid printing requires specialized printers—most office printers handle Letter and Legal but not Tabloid. The larger size makes documents impressive but less portable and more expensive to produce. Consider whether your audience has appropriate printing capability before choosing Tabloid size.

A3 (297 × 420 mm)

A3 is the international equivalent of Tabloid, exactly twice the size of A4 at 297 × 420 millimeters (11.69 × 16.54 inches). It's widely used outside North America for large-format documents, presentations, and technical drawings. A3 maintains the same 1:√2 aspect ratio as all A-series sizes, ensuring consistent proportions across scales. Many office copiers and printers in Europe and Asia support A3, though it's less common than A4. Like Tabloid, A3 provides impressive presentation but requires specialized printing equipment.

Understanding the A-Series System

The Mathematical Foundation

The ISO A-series is built on elegant mathematics. A0 is the largest common size at exactly one square meter (841 × 1189 mm). Each smaller size halves the larger one: A1 is half of A0, A2 is half of A1, and so on. This halving maintains the 1:√2 aspect ratio across all sizes, so folded pages have the same proportions as unfolded ones. A4 is four steps down from A0 (16 times smaller). This system enables efficient printing and paper use—two A5 pages fit perfectly on one A4 sheet, four A6 pages on A5, etc.

Common A-Series Sizes

Understanding the range helps choose appropriate sizes. A3 (297 × 420 mm) is used for posters, presentations, and large documents. A4 (210 × 297 mm) is the standard document size internationally. A5 (148 × 210 mm) suits booklets, notepads, and small publications. A6 (105 × 148 mm) is used for postcards and pocket-size materials. A7 (74 × 105 mm) and smaller serve specialized purposes like business cards or note cards. Each size serves specific document types while maintaining consistent proportions.

Regional Differences and Standards

North America vs. International

The Letter versus A4 divide creates real challenges in global business. North American organizations default to Letter size, while international partners expect A4. Templates and forms designed for one size often look wrong when printed on the other. Margins that work perfectly on Letter create text too close to edges on A4, or vice versa. Content that fits on one Letter page might extend to two A4 pages or leave awkward whitespace. International PDF distribution should consider target audience's expected page size and provide appropriate versions or flexible layouts that work acceptably on both.

When to Choose Which Standard

Select page size based on your primary audience and purpose. Use Letter for U.S. and Canadian audiences, U.S. government submissions, and distribution within North America. Use A4 for international audiences, European and Asian distribution, and compliance with ISO standards. Use Legal for U.S. legal documents, court filings, and contracts where expected by recipients. Use A3 or Tabloid for presentations, posters, or technical drawings requiring larger format. For truly international distribution, design flexible layouts that work acceptably on both Letter and A4, or provide both versions.

Custom and Specialized Page Sizes

When Custom Sizes Make Sense

Standard sizes don't suit all purposes. Books often use specific trim sizes optimized for their content and market (6 × 9 inches for trade paperbacks, 5.5 × 8.5 for mass market). Marketing materials use custom sizes for distinctive appearance and shelf presence. Technical documentation may require unusual proportions for fold-out diagrams or reference guides. Digital-only PDFs can use any size optimized for screen viewing rather than paper constraints. Custom sizes enable perfect fit for specific purposes rather than forcing content into standard formats.

Common Custom Sizes

Several non-standard sizes appear frequently. Square formats (8 × 8 inches) suit photo books and creative layouts. Brochure sizes (8.5 × 11 folded to 8.5 × 3.67 inches) serve marketing materials. Business cards (3.5 × 2 inches in U.S., 85 × 55 mm internationally) have standardized custom sizes. Envelopes follow specific size standards separate from paper sizes. Screen-optimized sizes (16:9 aspect ratio) match display proportions for presentation PDFs. Each custom size serves specific needs that standard formats don't address.

Creating Custom-Sized PDFs

Most PDF creation tools support custom page dimensions. Specify exact width and height in your preferred units (inches, millimeters, points). Consider whether custom size documents will ever be printed—printers may not handle unusual sizes well. Account for bleed if content extends to page edges (add extra margin beyond final trim size). Design with final use in mind: screen viewing versus printing affects optimal dimensions. Test custom-sized PDFs on target devices or printers to verify they work as intended.

Converting Between Page Sizes

Scaling Content

Converting PDFs between page sizes requires careful handling. Fit-to-page scaling shrinks or enlarges content to fit the new size, potentially making text too small or images pixelated. Crop-to-size maintains original scale but may cut off content that extends beyond new page boundaries. Reflow content adapts to new page dimensions by adjusting text layout—works only for reflowable content, not fixed-layout PDFs. Choose scaling approach based on content type and quality requirements.

Margin Adjustments

Different page sizes require different margin settings. Letter to A4 conversion needs narrower left/right margins (A4 is narrower) but can use similar top/bottom margins. A4 to Letter allows wider margins but may need content adjustment for the shorter page. Legal to Letter requires significant vertical compression or content splitting. Always preview converted documents to verify margins look appropriate and content isn't awkwardly positioned or cut off.

Quality Considerations

Size conversion affects document quality in various ways. Scaling up enlarges everything including any imperfections or low-resolution images. Scaling down can make small text illegible. Vector content (text, vector graphics) scales cleanly in either direction. Raster images (photos, scans) may appear fuzzy when enlarged significantly. Maintain original files at highest quality and largest size you'll need, then scale down for smaller sizes rather than enlarging from small originals.

Printing Considerations

Printer Paper Compatibility

PDFs must match available paper sizes for successful printing. Home and office printers in North America default to Letter, with Legal support common but not universal. European and Asian printers default to A4, often with A3 support in office environments. Tabloid and A3 require specialized larger-format printers. Check your target audience's typical printer capabilities before choosing page size. PDFs in unexpected sizes cause printing errors, scaling problems, or wasted paper from incorrect size selection.

Print Scaling and Fitting

Most PDF readers offer print scaling options to handle size mismatches. "Fit to printable area" scales content to fill available paper while maintaining aspect ratio—results in slightly smaller output if PDF size doesn't match paper. "Actual size" prints without scaling, potentially cutting off content extending beyond paper edges. "Shrink oversized pages" reduces content only if necessary to fit paper. Choose appropriate scaling when creating PDFs: design for actual expected printer size rather than relying on users to scale correctly.

Bleed and Trim Marks

Professional printing often requires bleed—content extending beyond final page edges. Bleed prevents white lines at page edges if cutting isn't perfectly precise. Standard bleed is 0.125 inches (3 mm) beyond final trim size. PDFs for commercial printing should include bleed area outside final page dimensions. Trim marks show printers exactly where to cut. Crop marks indicate final page boundaries. Design page size in your PDF creation software to include bleed area plus trim marks if needed for professional printing.

Digital Viewing Optimization

Screen Aspect Ratios

Page size affects PDF viewing experience on screens. Standard page sizes (Letter, A4) are taller than wide, matching portrait phone orientation but wasting space on landscape monitors. Widescreen PDFs (16:9 or 16:10 aspect ratios) fill laptop and desktop screens efficiently. Presentation PDFs benefit from landscape orientation matching projector ratios. Consider primary viewing context: phones favor portrait, laptops favor landscape, tablets work either way. Digital-only PDFs can optimize for screens rather than following print-based size standards.

Responsive and Flexible Layouts

Some PDF workflows benefit from flexible approaches. Create PDFs with generous margins that work acceptably on both Letter and A4. Design content in modules that reflow gracefully regardless of page size. Avoid hard-coded page references ("see page 5") that change if page size affects content flow. Test PDFs on multiple page sizes during design to ensure acceptable appearance across sizes. While PDFs aren't as flexible as HTML, thoughtful design accommodates size variation better than rigid, single-size optimization.

Common Page Size Problems

Mixed Sizes in Single Documents

PDFs sometimes contain multiple page sizes in one file. This occurs when merging files with different sizes, inserting pages from various sources, or intentionally including fold-out pages. Mixed sizes create printing challenges—printers may scale inconsistently or prompt for paper changes between pages. Digital readers handle mixed sizes poorly with jarring size changes during scrolling. When possible, standardize all pages to a single size. If mixed sizes are necessary, group same-size pages together and clearly indicate size changes to users.

Size Metadata Errors

Sometimes PDFs report incorrect page sizes in their metadata. Content designed for Letter appears as A4 or vice versa. Custom sizes display as standard sizes. These errors cause printing and viewing problems. Verify actual versus reported page size by checking document properties and comparing to known reference sizes. Recreate PDFs with correct size metadata if errors persist. Proper page size metadata ensures PDF readers and printers handle documents correctly.

Best Practices

Choosing Page Size During Creation

Set page size intentionally rather than accepting defaults. Consider your primary audience's location and expectations. Think about printing needs—will recipients print these PDFs? Account for distribution channels— email, web download, professional printing. Plan for archive and long-term access requirements. Setting correct size initially prevents later conversion headaches and quality compromises.

Documenting Size Requirements

For documents others will use, clearly specify page size requirements. Templates should state expected size prominently. Submission guidelines should specify accepted page sizes. Print service orders must include explicit size specifications. International collaboration benefits from discussing page size expectations early. Clear communication about page size prevents mismatches and rework.

Testing Across Sizes

Before finalizing important PDFs, test on relevant page sizes. Print test pages on available paper sizes. View on different devices with various screen sizes. Verify margins and spacing look appropriate. Check that critical content isn't cut off or awkwardly positioned. Testing catches size-related problems before distribution when fixes are easy rather than after when they're embarrassing.

Conclusion

PDF page sizes significantly impact document usability across printing, viewing, and international contexts. Understanding standard sizes—Letter for North America, A4 internationally, Legal for U.S. legal documents, and larger formats for presentations—enables appropriate choices for your specific needs. The mathematical elegance of the A-series system contrasts with North American standards, creating challenges for global distribution. Custom sizes serve specialized purposes but require careful consideration of printing and viewing implications. When converting between sizes, attention to scaling, margins, and quality preserves document integrity. Choose page sizes thoughtfully based on audience, purpose, and distribution context rather than accepting defaults, and your PDFs will work correctly wherever they're used.