Compressing a PDF without losing the parts you need
Understand why scanned PDFs shrink and why selectable text may disappear.
A PDF with scanned photographs behaves differently from a PDF exported from a word processor. A scan stores pixels for almost every point on every page. A text PDF usually stores compact instructions to draw letters. Re-encoding the scan can make a large difference; re-encoding text pages as pictures may make them less useful.
Start by identifying the document
Open the original PDF and try selecting one sentence. If you can copy the sentence into another app, it is probably a text PDF. If you can only select the whole page as an image, it is probably scanned. This quick check is not perfect, but it helps you choose a compression approach.
The Compress PDF tool draws each page and stores the result as an image in a new PDF. It offers Low, Medium and High presets. Because the new pages are images, selectable and searchable text in the original is lost. Keep the original when you need copying, searching or accessibility.
Example: submitting a scanned certificate
- Make a copy of the certificate and note the upload site's size limit.
- Try Medium first. Download the result and compare the displayed before and after sizes.
- Zoom in on names, dates, stamps and small print. If they are unclear, try High. If the file remains too large, Low may help, but inspect it even more carefully.
Some already compressed PDFs will not get smaller. In that case, this tool keeps the original file rather than giving you a larger replacement. A promised exact size would be misleading: the result depends on the page count, image detail and selected quality. A strict upload limit may require reducing the scan resolution when making the original scan.
Before sending the file
Reopen the downloaded PDF. Count the pages, verify orientation and inspect a representative page plus the smallest text. If the recipient requires a searchable PDF, keep the text original or use a compression method that preserves PDF text instead of rendering pages as images.