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Make All PDF Pages Same Size is a free browser tool that finds the pages in a PDF whose dimensions do not match the rest and converts the whole document to a single page size. It measures every page on upload and reports the result in one line, for example "17 pages are A4, 3 pages have different dimensions", together with a table showing each size and the exact page numbers that use it. A single click applies the most common size to the entire file. Mixed page sizes are the normal outcome of ordinary work: a contract printed and scanned on a flatbed, a report where an A3 chart was inserted into an A4 document, a bundle merged from files created in different countries where A4 and Letter both appear, or a scan whose pages were cropped slightly differently by the scanner software. ISO 216, the standard behind the A series, and the North American ANSI sizes were defined independently, so A4 and Letter differ by about 6 mm in width and 13 mm in height and will never line up. The document opens fine, so the problem only shows up later, when a print job scales half the pages, an upload portal rejects the file, or a page jumps in size while scrolling. The tool offers four ways to choose the target: A4, Letter, the size most pages already use, the largest page in the file, or a custom width and height in millimetres or points. Content is then either scaled to fill the new page or kept at its original scale and centred with white space added around it. Landscape pages can keep their orientation, so a wide table does not shrink into a portrait frame. Everything runs locally using pdf-lib and pdf.js, so scanned contracts, medical records and financial statements never leave the device. In a wider workflow, PDF Crop & Resize handles cropping margins and resizing a single chosen page range, PDF Merger combines files before normalising them, and PDF Rotate fixes pages that are simply turned the wrong way.
The reason inconsistent page sizes are so annoying is that nothing warns you about them. A PDF viewer happily renders a file where page 4 is Letter and the rest are A4, and the difference is only 6 mm wider and 13 mm shorter, which is invisible on screen. The cost arrives at the end of the process: a print driver set to "actual size" produces pages with different margins, a duplex job feeds wrongly, a submission portal that validates page dimensions rejects the upload, or a reader sees the page jump as it scrolls. Most PDF services offer resize, crop and compress as separate operations and leave the diagnosis to the user, which is the hard part. This tool inverts that order. It measures first, tells you in plain language what it found, and offers one button that applies the obvious fix. Only if you want something else do the other options matter. A few practical notes. Scanned pages rarely match a standard format to the decimal, so sizes within roughly 0.7 mm of each other are treated as the same format rather than reported as separate groups; this keeps the summary honest instead of listing twenty near-identical sizes. Pages carrying a rotation flag are measured as the reader sees them, so a portrait page rotated 90 degrees is correctly grouped with the landscape pages. The output is a standard PDF that opens in Acrobat, Preview, Chrome and any mobile reader, with text, fonts, links and images preserved. If your real problem is uneven white margins rather than uneven page sizes, PDF Crop & Resize is the better tool, since it trims the margins directly. If pages came from several source files, run PDF Merger first and normalise the combined document in one pass, and use PDF Page Count Checker to confirm the final file has every page you expect.