How to Compress a Very Large PDF (50MB, 100MB or More)
Most PDFs are small. But a scanned book, a long presentation or a report full of photos can easily reach 50MB, 100MB or more, and then email, upload forms and many online tools refuse it. The good news is that very large PDFs usually shrink by a lot, because the size comes almost entirely from pictures.
Step 1: find out why it is big
| What the PDF contains | Typical size | How much it can shrink |
|---|---|---|
| Text only | A few MB at most | Very little |
| Photos and graphics | Large | A lot |
| A scan of many pages (every page is a picture) | Very large | A lot |
| A scan at 600 dpi | Huge | The most |
If your file is a scan, the page count and the scanning resolution decide the size. A 100-page scan at 600 dpi is far bigger than the same pages at 150 dpi, and for reading and printing text the lower resolution is usually fine.
Step 2: check what your account allows
The largest file you can upload depends on your account: guests can upload smaller files than signed-in users, and paid plans allow larger ones. The Pricing page shows the size limit for each plan. If your file is over your limit, go straight to step 5 and split it first.
Step 3: compress in the right order
- Open the Compress PDF tool and add the file.
- Start with Recommended. It is enough for most files.
- Check the size on the result page. If it is still too big, run the original again on Strong.
- For a black-and-white scan, switch on Convert colours to grey. On scans this can save a great deal, but it removes colour, so skip it for colour photos.
Always compress the original file, not a result that was already compressed, to avoid stacking quality loss.
Step 4: remove what you do not need
Fewer pages mean a smaller file. Delete blank or irrelevant pages with Remove pages, or keep only what is needed with Extract pages. Our guide to removing pages explains the options.
Step 5: split it when nothing else is enough
If a portal accepts several files, or you are sending the document in parts anyway, split the PDF into sections first and compress each one. This is also the way to handle a file that is larger than your account allows: split it, then compress the parts. See our guide to splitting a PDF.
Step 6: fix the source when you can
If you still have the original document, you can often make a much smaller PDF from the start:
- Reduce the size of pictures in Word or PowerPoint before exporting.
- Scan at 150 to 200 dpi, not 600.
- Scan in black and white or grey when colour is not needed.
- Do not paste uncompressed photos straight from a camera.
Do not forget the limits of where you are sending it
Email services and upload portals each have their own limit, and they are often lower than you expect. We list the official ones for Gmail, Outlook, Yahoo, iCloud, Proton, USCIS and IRCC on our PDF size limits page, and the basic steps for getting under 1MB, 500KB or 200KB are in our guide to reducing PDF size.
Tips
- Large scans take longer to upload on a slow connection, so give it time.
- Keep the original file safe until you have checked the compressed one.
- After compressing, open the result and look at a few pages, especially photos and small print.
- If the scan has no searchable text, make it searchable with OCR PDF (see our OCR guide).
Is my file safe?
Your file is encrypted in transit and at rest and deleted automatically, by default within 2 hours. See the privacy page.
Frequently asked questions
What is the biggest PDF I can upload to SnapPDF?
The limit depends on your account: guests can upload smaller files than signed-in users, and paid plans allow larger ones. The Pricing page lists the file size for each plan.
Why is my PDF so large?
Almost always because of images: a scan of many pages, high-resolution photos, or a presentation full of pictures. Text takes very little space.
What if the file is still too big after compressing?
Convert black-and-white scans to grey, remove pages you do not need, or split the file into parts and compress each one.
Will compressing damage the text?
No. Compression works on the images inside the PDF. Text stays sharp, but photos and scans lose some detail on the strongest setting.