Three levels, and what each one really does
Every PDF compressor has to make the same trade-off: smaller file or perfect quality. We'd rather tell you exactly what's going on than hide it behind a slider, so here it is.
Light (lossless clean-up)
This rebuilds the PDF more efficiently. It drops leftover junk, packs the internal structure tighter and removes duplicate bits. Nothing about how the pages look changes, and text stays selectable and searchable. The catch: savings are usually small, anywhere from almost nothing to maybe 20 percent. Files made by old scanners or exported from some apps can shrink more.
Medium
This redraws every page as a high-quality image and builds a fresh PDF from those images. For scans and photo-heavy files, the size often drops by half or more and it still looks great on screen and on paper.
Strong
Same idea as Medium, but with lower resolution and stronger JPEG compression. This is the "I need this under 2MB and I don't care how" option. Fine print and thin lines can get a little soft, so zoom in and check before you send it.
The honest catch with Medium and Strong
Because those two levels turn each page into a picture, the text stops being real text. You won't be able to select it, copy it or search it with Ctrl+F, and fillable form fields and links go away too. For a scanned document, that doesn't matter, since it was already a picture. For a typed report or a contract you need to copy from, use Light, or keep your original file alongside the compressed one.
Why are PDFs so big in the first place?
- Scans. A phone or office scanner set to 600 DPI color makes enormous pages. One page can easily be 3 to 5MB.
- Photos. A PDF with a dozen full-resolution phone pictures dropped into it carries all those megapixels along.
- Embedded fonts. Some apps embed entire font files, even for a one-page flyer.
- Merging. Combining files adds their sizes together. Five 6MB files make a 30MB PDF.
If your file is mostly scans or photos, Medium will do wonders. If it's mostly text, it's probably not that big to begin with, and Light is all you need.
Common size limits to aim for
Gmail attachments top out around 25MB, Outlook.com is around 20MB, and lots of job sites, school portals and government upload forms cap files at 5MB, 2MB or even 1MB. We show you the new size right away, so you know if you made it under the bar. Lots more tips in how to reduce PDF size for email.
Tips to get smaller files
- Delete pages you don't need first. A blank back page from a duplex scan still costs space. Trim them with Delete PDF pages.
- Split before you send. If one file is still too big, split it into two attachments.
- Scan smarter next time. 200 to 300 DPI is plenty for documents, and grayscale is a lot smaller than color.
- Try Medium before Strong. It's often enough, and it looks noticeably better.
Nothing gets uploaded
Compression runs on your device, in your browser. That's why a really big file can take a little while on an older phone, since your phone is doing the work instead of a server. The upside is that your documents never leave your hands.