Change PDF file size

A form wants a number, so give it a number

Court filing portals, job application forms, visa systems and university upload pages all cap the file size, and they refuse the upload without telling you how far over you are. A slider marked medium is no help against that. You need the output to land under a specific count of bytes.

The compress tool takes the number directly. Type 500 in the KB box, or switch the unit to MB and type 1. The unit switch treats 1 MB as 1,024 KB, so a 1 MB target is 1,048,576 bytes.

Watch out for the other kilobyte. Some upload forms count 1 KB as a flat 1,000 bytes, which makes their cap 2.4% tighter than the same number here. If a file that looks correct still gets rejected, drop the target by 3% and run it again. The extra cut is invisible on the page.

The size buttons hide themselves for a reason

The tool never offers a target that is larger than the file you gave it. Load a 300 KB document and the 500 KB and 1 MB buttons disappear, because compressing to a size the file already beats is a no-op that would waste your time and tell you nothing.

This also means the tool cannot make a PDF bigger. Nothing here pads a file with filler bytes to satisfy a minimum size rule. If a form demands a floor rather than a ceiling, the guide to increasing a PDF's file size covers what actually gets a file over a minimum and what each route costs, and none of it is a compression setting.

How the tool gets under your number

Four methods race for your target, and the smallest verified file wins. For a tight number the tool also offers a smallest setting, which redraws the pages harder while keeping every word selectable. The result names the size it reached, so you can see the margin before you upload.

Page count is the other lever. Dropping two pages of photography from a long document saves more than any setting, and organize pages does that in the same browser tab.

Which number to ask for

Which number to type depends on what the receiving system actually asked for.

• A hard cap. Use it exactly. Choosing 100 KB when the form allows 2 MB throws away quality for nothing.
• A guideline. Pick the largest size that still clears it, because every KB you leave unused is detail you keep on the page.
• No rule at all. Do not type a number. Run the tool with no target and the lossless methods do the work: the document gets rebuilt and its embedded fonts get subsetted, which changes no pixels and no characters.

Then check the size the receiving system reports back, not the size your file manager shows. Mail systems encode attachments, which adds about a third to the transmitted size. A 1 MB PDF can arrive as a 1.37 MB attachment and trip a limit the PDF itself never came near.

What fits under a given number

The public run covered 16 targets, from 20 KB to 10 MB, on 114 public documents, and every case produced a verified file. At the smallest setting a text page comes down to about 14 KB and a phone photo of a page to about 18 KB, so 1 MB holds about 70 text pages or about 55 photographed ones.

A scanned page is pixels, and the tool keeps a black and white page as a sharp 1-bit image at 150 dpi, about 29 KB a page.

The general compression guide covers what is making your file heavy in the first place, which decides how many pages fit under the number. The compress hub lists the rest.

One page per number

Each cap a form is likely to name has its own page, and each page says how many pages fit at its own number.