Compress a PDF to 500 KB without uploading it

Who asks for 500 KB

The 500 KB limit is typical of university applications, visa forms and tender portals with a 500 KB attachment limit. At this size most text documents with a few photos, or a scanned document of six to ten pages at Strong or Extreme fit. The tool does not pad or pretend: when a document cannot get under the target it tells you what the floor is, so you know whether removing pages, splitting the file or scanning again at a lower resolution is the way to go.

What the tool changes

Every embedded photo, screenshot and scan is decoded and re-encoded as JPEG, with its longest side capped, at the first level that fits under 500 KB. Text, fonts and vector drawings are left as they are, so the result stays sharp and searchable. Images are only replaced when the new version is smaller, images with transparency keep their mask and are not downsampled, and CMYK, JPEG 2000, fax and JBIG2 scans are skipped and listed on the result card.

• Level ladder: quality 85 and 2400 px down to quality 35 and 600 px, in eight steps
• Stops at the first level under the target, so quality is only lowered as far as necessary
• Nothing is uploaded; the work runs in your browser with pdf-lib and the canvas encoder

How many pages fit

A page of plain text is 20 to 60 KB. Scans are the expensive part: about 60 to 120 KB per scanned page at Strong, so a six-page scan usually fits. If the result card shows that the smallest file is still above 500 KB, use Delete PDF Pages to drop blank or duplicate pages, or Split PDF to send the document in parts that each fit.

Check before you submit

The preview panel renders page one of the actual output, not an estimate, so you can judge legibility before downloading. Portals that count size in kibibytes versus kilobytes differ by about 2%; PaperKit measures 1 KB as 1024 bytes, which is the stricter reading, so a file that fits here fits either way. Keep the original until the upload is accepted.

Other sizes and related steps

The same tool targets any size you type, from 10 KB upwards, and offers Light, Balanced, Strong and Extreme levels when there is no hard limit. Remove PDF Metadata strips author and software fields if the submission is anonymous, and Compress Image handles single JPG or PNG files that a form wants on their own.