More about the Resize PDF
Fit inside vs Fill page, the one choice that matters
Fit inside scales each page so the whole page stays visible, which can leave margins on the new paper size. It is the safe default: nothing gets cut off, and a US Letter report moved to A4 just gains slim margins.
Fill page scales until the paper is completely covered, which can crop the page edges. Use it when the paper must look full, a poster, a presentation handout, and check the edges afterwards. When in doubt, Fit inside.
Auto orientation, explained
Auto keeps each page's current orientation on the new paper size: portrait pages stay portrait, landscape pages stay landscape. It is the right choice for mixed documents, like a report with a few landscape tables.
Choose Portrait or Landscape only when you want to force every page to one orientation, for example, making a whole document print ready on portrait A4. Forced orientation on a landscape table page will shrink it to fit, so preview the result.
The Letter-to-A4 dance
This is the single most common resize in the world: a US Letter document (8.5 × 11 in) that must print on A4 (210 × 297 mm), or vice versa for international clients. The sizes are close but not identical, so pick the target size, keep Auto orientation and Fit inside, and every page lands neatly centered.
Why do pages end up mixed in the first place? Usually scans (every scanner has its own idea of page size) or merged documents from different sources. Standardizing fixes the printing and makes the file look like one document instead of three stapled together.
Resizing for print shops
If a printer asks for a specific size, give them exactly that, do not assume 'close enough'. A4 and Letter differ by 6 mm in width; on a commercial press that is the difference between fitting and reflow.
Export the resized file with a clear name (report-A4.pdf) and keep the original. If the printer comes back with a correction, you re export from the original rather than resizing a resize.
What resizing cannot fix
It standardizes page size; it does not fix content. A low resolution scan stays low resolution, just on a tidier page. Crooked scans stay crooked. Margins that were wrong stay wrong. They are just consistently wrong now.
For content problems, fix the source: re-scan straight, or edit the original document. Resizing is presentation, not repair.
Resizing for specific printers
Office printers usually handle A4 and Letter interchangeably, but production printers and print shops do not. They need the exact size. When a printer specifies 'A4, no bleed' or 'Letter, 0.5in margins', resize to exactly that before sending.
Include the size in the filename (brochure-A4.pdf). Printers juggle dozens of files daily; a filename that states the size prevents the 'is this the A4 one?' email.
And always keep the original. If the printer reports an issue, you troubleshoot from the source, not from a file that has already been resized once.
Resizing and print bleed
Professional printing needs 'bleed', extra image area beyond the trim edge (usually 3mm/0.125in) that gets cut off. If your printer asks for 'A4 with bleed', they want a slightly LARGER page, not exactly A4.
This tool resizes the page box; it does not add bleed artwork. For proper bleed, set it up in your design software before exporting. Resizing here is for fitting existing content to standard sizes, not for prepress.
If you are unsure whether you need bleed, ask the printer. For office and home printing, you never do, bleed is strictly a commercial print shop concept.
Resizing scanned documents
Scans resized to smaller page sizes often become unreadable, the text was captured at a fixed resolution, and shrinking the page shrinks the text. If a scan must be resized smaller, check legibility at 100% zoom before distributing.
For scans that must be larger (a receipt scan printed for records), resizing up does not add detail. It just makes the pixels bigger. Acceptable for filing, but do not expect sharper text.
When possible, rescan at the needed size rather than resizing the PDF. The scanner captures fresh detail; the resizer only stretches what is there.
The maths of a Letter page landing on A4
A US Letter page measures 612 by 792 points; A4 is 595 by 842 points, narrower, but taller. With Fit inside, the scale factor is the smaller ratio: 595 divided by 612 is about 0.972, against 842 divided by 792 at about 1.063, so width governs and content scales to 97.2 percent, landing at 595 by 770 points, centred, with 36 point margins, about 12.7 millimetres, top and bottom.
Shrinking a full paper size shows the sharper edge of the maths. An A3 page resized to A4 scales by about 0.707 in each direction, halving the area, so 12 point text prints at an effective 8.5 points. Fine print and drawing annotations can drop below comfortable reading size, so whenever you shrink by a full size, check the smallest text at 100 percent zoom before sending the file anywhere.
Resize, compress or crop: picking the right fix
These three tools are constantly confused. Resize when the paper size is the problem: pages printing cropped, mixed sizes in one document, a file rejected for being Letter instead of A4. Compress when file weight is the problem, the pages look right but the document is too heavy to email. Crop when the content has unwanted edges, such as scanner borders or excess white space. Each fixes a different layer.
Two mistakes follow. The first is resizing an already resized file: each pass scales the content again inside fresh margins, so a twice resized document ends up with small text floating in white space. Always start from the original. The second is choosing Fill page for a text document to make it look fuller. Fill crops whatever overflows, and what overflows first is page numbers, headers and the outer words of wide tables.
