Compress a PDF to a specific size in KB or MB

Every page is drawn at a chosen resolution (DPI), saved as a JPEG image and put into a new PDF with the same page dimensions. The tool looks for settings where the file fits the limit and the pages keep as much detail as possible. The size of each attempt is the real size of the saved file, not an estimate.

1. It first tries the lowest settings: 72 DPI and JPEG quality 30%. If the file does not fit even then, the limit is out of reach and you get that smallest result with a message.
2. Then it uses a binary search to find the highest DPI from the list 72, 84, 96, 110, 130, 150 and 200 at which the file fits with quality 75%.
3. Finally it tunes the JPEG quality in 5-point steps: up to 95% at the chosen DPI, or down to 30% when even 72 DPI at 75% is too big.

A typical run takes between a few and eight attempts. Each one renders every page, and attempts that already go over the limit stop early. A long document can take a few minutes. Very large pages are capped at about 16 megapixels so the browser does not run out of memory.

Pages become images, so text can no longer be selected, copied or searched, and links, bookmarks and form fields stop working. Page dimensions (for example A4) stay the same. The result is a new file, so it is not password-protected and does not carry the original metadata.

Do not use this method for documents you still need to edit, search or fill in. Keep the original and send the smaller copy only where a size limit forces you to.

The size of the result depends mostly on the number of pages, so it helps to work out how much room each page gets. The table shows the limit divided by the number of pages, in KB per page.

The tool warns you when a page gets less than 100 KB (resolution and quality will be low and small text may blur), and more strongly when it gets less than 40 KB (the limit may be out of reach). This is only a rough estimate. In our tests an A4 page saved at the lowest settings (72 DPI, quality 30%) weighed from about 40 KB (text with a photo) to about 95 KB (densely set text), and a page with a plain background weighs much less.

If you do not need an exact size, use Compress PDF. It has three ready-made levels and shows the result right away, so for a file that is only slightly too big “Recommended” is often enough. That tool also turns pages into images, so it has the same limitations as this one.

A document built from photos shrinks better if you shrink the photos before you assemble the PDF. Do that in compress image to target size, then put the pages together in JPG to PDF. You can also split a long document and send the parts separately.

The tool counts 1 KB as 1000 bytes and 1 MB as 1,000,000 bytes. Some forms count 1 KB as 1024 bytes. A result that fits a limit counted the first way also fits there, with room to spare. If a form rejects a file right at the limit, set the limit a few KB lower.