Nothing like hitting Send and getting a "message too large" bounce ten minutes later. Big PDFs are almost always big for one of a few fixable reasons. Let's figure out how small you need to go, then get you there.
How small does it need to be?
Limits change from time to time, but roughly:
- Gmail: around 25MB for attachments. Bigger files get turned into a Google Drive link instead.
- Outlook.com: around 20MB for regular attachments. Work Outlook accounts are set by your company and are often smaller, 10MB is common.
- Yahoo Mail: around 25MB.
- iCloud Mail: around 20MB, with Mail Drop for bigger files.
- Upload forms (job applications, school portals, government sites, insurance claims): often 10MB, 5MB, 2MB or even 1MB. It's usually printed right next to the upload button.
One sneaky detail: email attachments get encoded when they're sent, which makes them about a third bigger on the way out. So a 20MB PDF can actually blow past a 25MB limit. Aim for comfortably under.
Why is my PDF so big?
Almost always it's one of these:
- It's a scan. Scanners and scanning apps set to high resolution and full color make giant pages. A 10-page scan can easily be 30MB.
- It has photos in it. A modern phone photo is 3 to 6MB. Drop a dozen into a document and do the math.
- You merged a bunch of files. Merging adds sizes together.
- It was exported with "high quality print" settings from Word, PowerPoint or a design app.
Text-only PDFs are rarely the problem. A 50-page typed report is usually well under 1MB.
Step 1: Remove what you don't need
The cheapest megabyte is the one you don't send. Before compressing anything:
- Delete blank pages, cover sheets and duplicate pages with Delete PDF pages.
- If they only need a few pages, send just those with Extract PDF pages.
Step 2: Compress it
Open Compress PDF and drop your file in. You've got three levels:
- Light cleans up the file without changing how anything looks. Small savings, but text stays selectable. Try this first on typed documents.
- Medium redraws every page as a good-quality image. Big savings on scans and photo-heavy PDFs, often 50 to 80 percent. Looks great on screen and printed. Text won't be selectable afterward.
- Strong squeezes harder for those brutal 1MB or 2MB upload limits. Zoom in and check that the fine print is still readable before you send.
You see the before and after size right away, so you know if you made it. Not small enough? Try the next level up.
A quick before-and-after example
Say you scanned a 12-page lease on your phone at the app's highest setting and ended up with a 38MB PDF. Light compression might only get it to 35MB, since a scan is all images. Medium will typically bring it down to somewhere around 4 to 8MB, which looks just as good on screen. If the landlord's portal has a 2MB limit, Strong usually gets you there, but zoom in on the fine print before you send it.
Step 3: Still too big? Split it
If a 200-page scan won't get under 25MB no matter what, split it into two or three parts and send them as separate emails ("Part 1 of 3"). Most people would rather get three emails than a cloud link that asks them to sign in.
Step 4: Or skip the attachment
For really big files, a share link from Google Drive, OneDrive, iCloud Drive or Dropbox is the cleanest option. Upload the PDF there, share a link, paste it into your email. Just be aware that this does put your file on that company's servers, and double-check the link's sharing settings so it's not open to the whole internet.
Prevent giant PDFs next time
- Scan at 200 to 300 DPI, not 600. For documents, 300 DPI is plenty, even for printing.
- Scan in grayscale unless color really matters. It's a fraction of the size.
- In Word, use File, Save As, PDF and pick "Minimum size (publishing online)" when you don't need print quality.
- On a Mac, Preview's Export menu has a "Reduce File Size" Quartz filter. It's aggressive, but quick.
- Shrink photos before putting them into a document. Most phones can share a photo at a smaller size.
A quick word on privacy
A lot of online compressors upload your file to their server to do the work. That's not great when the PDF is your tax return or medical records. JoinPDFs compresses right in your browser, so the file never leaves your device. If you're curious how to tell the difference, we wrote about it in is it safe to merge PDFs online?