Find out what makes it large
Almost all of a large PDF's size comes from images: scanned pages, photos and screenshots. Text takes very little space. A 40-page text document is often under 1 MB, while ten scanned pages can be 20 MB or more.
Compress the images inside the PDF
- Open Compress PDF.
- Choose Medium for a good balance, or Strong for the smallest file.
- Drop in the PDF, check the new size, and download it.
Photos and scans are recompressed and scaled down; text stays sharp and selectable. PDFs that are mostly text are already compact and barely shrink.
Remove pages you do not need
Blank pages, cover sheets and appendices add up. Remove PDF Pages deletes the ones you list and keeps the rest.
Split it into parts
If a file is still over an email limit (Gmail allows 25 MB of attachments), Split PDF can divide it into two or more smaller files by page range.
On a Mac: Preview
Open the PDF in Preview, choose File → Export, and set Quartz Filter to Reduce File Size. It shrinks files a lot, but can make images noticeably blurry, so check the result.
Start with the scan settings
If you are scanning the pages yourself, the scanner settings matter more than any compression afterwards. A text page scanned in color at 600 DPI can be ten times the size of the same page scanned in grayscale at 200 DPI, and the text is just as readable. Use color only for pages with photos or colored marks.
Common problems
- Compression barely changes the size. The PDF is mostly text, drawings or embedded fonts rather than photos. Fonts for Chinese, Japanese or Korean can take several megabytes on their own and cannot be compressed away.
- A color scan is still too large. Turning it into grayscale with Grayscale PDF often makes it much smaller, especially combined with compression.
- The text became hard to read. Use a lighter setting, or compress only the pages with photos by splitting them off first.