How to Reduce a PDF's File Size for Email

Most email providers cap attachments around 25MB, and a scanned document can blow past that surprisingly fast - a handful of pages scanned as photos, not text, can add up to well over 50MB. Here is why that happens and how to get it back under the limit.

Why scanned PDFs get so big

A page of actual text in a PDF is tiny - a few kilobytes. A page that is really a photograph of a page (which is what most scanning apps and phone cameras produce) is a full image, often at a far higher resolution than the page needs for reading on screen. A 20-page scan at high resolution can easily be ten times the size of the same 20 pages as real, selectable text.

Shrink it

• Open Compress PDF and drop in the file.
• It finds the images inside the PDF and recompresses them - this is where nearly all of a scanned PDF's size lives, so this step alone often gets a file most of the way to a usable size.
• If you know your limit, type it into the optional size box (say, 20 for a 20MB cap). Instead of a fixed preset, it tries the gentlest setting first and only gets harsher until the file fits - so you keep as much quality as the limit allows.
• Download and check the new size against your limit.

Fitting a tight limit can mean reducing image resolution, not just quality, and the result screen says when that happened. If the limit genuinely can't be met, it says that too rather than handing back a file that misses it.

If it is still too big

A very large scan sometimes needs a second step: splitting it into parts with Split PDF and sending it as two emails, or sharing a link instead of an attachment. Compression reduces size without removing pages - splitting is the option when there is simply more content than any single email can carry.

Common questions

Will this work on every PDF? It helps most on photo-heavy or scanned PDFs. A PDF that is mostly real text has very little to compress in the first place, since text is already small.

Can compressing make a file bigger? An image is replaced only when its recompressed version is smaller, but the final PDF also includes document structure and, on the free tier, a Filevolo credit. Check the final size rather than assuming every document will shrink.

Is my file uploaded anywhere? No, compression happens entirely in your browser.