How to get a PDF under an upload size limit on a Mac
By Himanshu Ranjan · Updated 8 November 2026
To get a PDF under an upload limit on a Mac, run Compress › Compress under 10 MB, Compress › Email-safe (under 20 MB), Compress › Gmail-safe (under 25 MB) or Compress › Compress to size… in FileDial. They squeeze images step by step and split the file into parts if they cannot reach the target.
Pick the tool that matches the limit
A form that says maximum file size 10 MB is a hard wall: the upload fails or the page refuses it. Guessing at compression settings wastes tries. FileDial has tools that aim at a size instead of a quality: Compress › Compress under 10 MB, Compress › Email-safe (under 20 MB), Compress › Gmail-safe (under 25 MB), and Compress › Compress to size… for any other number.
Each of them squeezes images step by step until the file is under the target, and splits it into parts if it cannot get there. Your original is untouched, and the result card shows the size before and after.
- Portal limit of 10 MB: Compress under 10 MB.
- Email attachment around 20 MB: Email-safe.
- Gmail attachment cap of 25 MB: Gmail-safe.
- Any other limit: Compress to size…
Compress to a limit with FileDial
Choose the tool, run it, and read the result card.
- Select the PDF in Finder.
- Hold the right Option key to open the dial and choose the Compress category.
- Release on the tool that matches your limit, for example Compress › Compress under 10 MB.
- If you picked Compress to size…, enter the size you need.
- Check the result card for the new size, then open the PDF and read the pages with small print.
Leave margin under the limit
A portal that says 10 MB may count megabytes differently from the way you do, since some systems use 1,000,000 bytes and others 1,048,576. Aim a little under the cap. If a file is 9.9 MB by one measure, it may be over by another. Using Compress to size… with a slightly lower number than the limit avoids a second try.
Also consider total size when the form takes several files. If the limit applies to the whole submission, each file has to be smaller than you think.
What you give up
Hitting a size target is done by lowering image resolution and quality, so photos and scans get softer. Text stays selectable, as the compression tools' notes say, but a tiny signature or a stamp on a scan can become hard to read. Always look at the pages with the finest detail.
If one big image is the cause, shrinking that image is better than squeezing everything. Another cause is hundreds of pages of scans at high resolution; here, splitting into parts, which the tools do automatically if needed, may be a better answer than an unreadable single file.
If a target cannot be reached, the tool splits the PDF into parts, each under the size. That is often acceptable for email, but some portals accept only one file. In that case, remove pages you do not need with Organize › Delete pages…, or reduce scan resolution before merging. Or scan again at lower resolution. If sending is a problem for a huge archive, FileDial can also split into ZIP parts, which suit file-sharing sites with a cap.
A worked example: a visa application pack
A portal wants a single PDF under 10 MB, and your scanned pack is 58 MB because every page was scanned in color at high resolution. Run Compress › Compress under 10 MB. If it reports it had to split the file, do not upload the parts blindly; check whether the portal accepts several files. If not, convert the pack to grayscale with Convert › Grayscale PDF first, which often helps scans of black text, then compress again.
Finally, open the result and zoom in on the pages that matter most: dates of issue, stamps, signatures, passport numbers. If a figure is hard to read at 100 percent zoom, the recipient will struggle too; use a gentler tool such as Compress › Compress and delete pages you do not need.
Order of operations that saves time
Do the structural work before you compress: delete pages you do not need, rotate sideways scans, merge into one file. Compress last. Compressing and then merging means you are chasing size twice. And compress from the original, not from a copy that was already compressed, because each lossy pass loses a little more detail.
Keep a labelled folder: original, working copy, final upload copy. When the portal rejects the file at 3 a.m., you will be glad you can try again from the right place.
Honest alternatives on a Mac
Preview can reduce a PDF: open it, choose File › Export, pick Reduce File Size in the Quartz Filter pop-up and save. Apple warns the result may be lower quality than the original, and the final size depends on the options chosen. You cannot set a target size, so it may overshoot or undershoot, and users report it sometimes barely changes text-heavy files.
Upload limits tend to be on job, tax and visa portals, so the files carry personal data. A web compressor adds a second upload before the first. FileDial compresses locally; a 42 MB PDF took about 2 seconds in our test.
Questions
How do I get a PDF under 10 MB on a Mac?
Select it in Finder and run Compress › Compress under 10 MB in FileDial. It squeezes images step by step until the file is under 10 MB, or splits it into parts if it cannot get there. Check the pages afterwards, especially small print.
Why does a compressed PDF still look the same size?
Files full of text and vector drawings have little to shrink, because compression works on images. Preview's Reduce File Size can leave them almost unchanged. If a scan is the cause, a target-size tool in FileDial will lower image resolution until the target is met.
What happens if the PDF can't be compressed enough?
The target-size tools split it into parts, each under the size, in page order. If the portal allows only one file, delete unneeded pages with Organize › Delete pages…, or rescan at a lower resolution, then compress again from the original.