A document that looks perfectly normal on screen sometimes prints with content crowding one edge of the paper or a chunk missing off the bottom. Nine times out of ten, that's a page size mismatch, not a printer problem.
Why A4 and Letter aren't interchangeable
Letter (used primarily in the US, Canada, and a handful of other countries) measures 8.5 by 11 inches. A4 (the standard nearly everywhere else, including the UK, EU, and most of Asia) measures 210 by 297 millimeters — roughly 8.27 by 11.69 inches. The two aren't just labeled differently, they're genuinely different shapes: A4 is narrower and taller than Letter. A document laid out for one and printed on the other doesn't just scale awkwardly — content near the edges can run off the printable area entirely, or margins that were carefully set end up uneven once the page proportions no longer match what the document was designed for.
Where this actually causes problems
This shows up constantly with cross-border paperwork — a contract template built by a US company and filled out by a client in Germany, a form downloaded from a UK government site and printed by someone in the US, an academic paper formatted for a journal that expects a specific page size regardless of where the author is writing from. It also shows up when combining documents from different sources into one file: a merged PDF built from a mix of A4 and Letter pages will print with each page shifted slightly differently unless every page shares the same size.
What resizing actually does
Resizing a PDF page scales its content — text, images, everything — to fit a new page boundary, rather than cropping or stretching it unevenly. Done properly, proportions stay consistent; text that was readable at Letter size is still readable, just repositioned to fit A4's narrower, taller frame. This is different from cropping, which trims content at the edges without resizing what remains — resizing changes the target page dimensions and scales content to match, while cropping just changes which part of the existing content is visible.
Choosing the right size for the situation
If you know exactly who's printing the document and where, match their regional standard — Letter for the US, A4 for most everywhere else. Legal size (8.5 by 14 inches) is worth knowing about too, since it's still the expected format for certain US legal filings and contracts even though it's far less common day-to-day than Letter. If you're not sure who'll be printing it, a custom size lets you match a specific known requirement — for instance, matching an existing template's exact dimensions so a new page fits seamlessly into a document set that already exists.
Checking a document's current page size before resizing
Most PDF readers show a document's page dimensions somewhere in a properties or document-info panel, which is worth checking before assuming a resize is even necessary — a document that already matches the target size doesn't need touching, and resizing an already-correct document unnecessarily just adds a scaling step that has no visible benefit. This check matters most when you've received a file from an unknown source and aren't sure what size it was originally built for.
Resizing without a print shop or design software
DocZap's Resize PDF tool scales every page in a document to A4, Letter, Legal, or a custom size directly in your browser, preserving proportions rather than stretching content unevenly — and since it's all client-side, there's no need to install desktop publishing software or send the file to a print shop just to fix a page-size mismatch.
Try these DocZap tools