How to reduce the size of a PDF to send it by email
Why PDFs get heavy, which limits email services apply and how to shrink a file without losing quality.
Why is my PDF so big?
In almost every case the weight comes from images: scanned pages, photos taken with a phone or high-resolution graphics. A 20-page text document weighs a few hundred kilobytes, while the same document scanned at 600 dpi in colour can exceed 30 MB. Fonts embedded in full and duplicated images can add more.
The limits to keep in mind
Gmail and Outlook accept attachments up to about 20–25 MB, many company mail servers stop at 10 MB and public administration portals often require files under 2–5 MB. Remember that email encoding makes attachments about a third larger than the file on disk.
Step 1: check what takes up space
Open the document with the Analyse tool. If images represent more than half of the file, compression will be very effective; if most of the weight is fonts or text, the file is already close to its minimum.
Step 2: compress the images
Use Compress PDF with the Recommended level: images are recompressed while text stays sharp and selectable. For very large scans choose the Strong level and compare the size before and after.
Step 3: send only what is needed
If the file is still too big, split it and send only the relevant pages, or send it in two emails. For documents you scan yourself, the Black & white filter of the Scanner produces files ten times smaller than colour scans.
Privacy
Compression runs on your device: the document is never uploaded to a server, which matters when the file contains payslips, medical reports or IDs.