How to Reduce PDF File Size for Email (Under the Attachment Limit)
Quick answer
Gmail caps attachments at 25 MB and Outlook at 20 MB, and a PDF almost always exceeds that because of embedded images rather than its text. Open Compress PDF on Auto, check the result, and re-run at Smallest if it is still over — for a document you are emailing rather than printing, Smallest is usually visually fine. If a large scan still will not fit, split it into smaller files or share a cloud link instead.
Why your PDF is too big to email
Most email providers cap attachments at around 20–25 MB (Gmail is 25 MB, Outlook 20 MB). A PDF blows past that almost always because of embedded images — scanned pages, screenshots, or high-resolution photos — rather than the text, which is tiny by comparison.
That's good news: compression works by recompressing those images, so the text stays perfectly sharp while the file shrinks.
Compress it to fit
Open Compress PDF and leave the quality on Auto — it inspects the document and picks a setting that suits it, which beats guessing. Check the result; if it's still over the limit, re-run at Smallest for the most aggressive reduction. For a document you're emailing rather than printing, Smallest is usually visually fine.
When compression alone isn't enough
If a huge scanned document still won't fit even at High, split it. Split PDF breaks it into smaller files — chapters, or a page range — that you can send across two emails or attach individually.
Another option for a very image-heavy file: convert the pages to JPG with PDF to JPG at a moderate resolution, which can land smaller than the source PDF, then share those. And for anything genuinely large, a shared cloud link avoids the attachment limit entirely.
Frequently asked questions
What are the actual attachment limits?
Gmail caps attachments at 25 MB and Outlook at 20 MB. Aim comfortably under whichever applies rather than just scraping beneath it, because encoding adds overhead in transit and a file that fits locally can still bounce.
Compression was not enough — what now?
Re-run the original at Smallest rather than compressing an already-compressed file, which gains very little. If it still will not fit, split the document and send it in parts, or share a cloud link and sidestep the attachment limit entirely.
Will the recipient notice the quality drop?
On a document being read rather than printed, rarely. Text is unaffected at every level because it is not re-rendered; what changes is detail in embedded images, which is far harder to notice on a screen than on paper.