How to Compress a Scanned PDF

When you scan a document, each page is captured as a photo and stored inside the PDF. A high-resolution color scan of a single page can be a megabyte or more on its own, so a multi-page scan grows fast.

Because the content is already an image rather than text, the file does not shrink by itself. To reduce it you need to re-encode those page images at a lower quality or resolution that is still easy to read.

If you have not scanned yet, a few settings help. Scanning in grayscale rather than color cuts the size sharply for documents that have no important color. A resolution of 200 to 300 DPI is plenty for text, and saving as PDF rather than a set of full-quality images keeps things compact.

For documents you have already scanned, you cannot change those settings after the fact, so the next step is to compress the finished PDF.

KiloPDF re-encodes the page images and searches for the quality and resolution that lands at your target size while keeping the pages readable. It does this in your browser, so a scanned ID, certificate, or statement is never uploaded.

Pick a target that suits where the file is going: a strict 100 KB or 200 KB for a portal upload, or a larger size like 500 KB when you want to keep more detail. Choose the file, set the target, and download.