How to get a PDF under 10 MB for an upload portal

To get a PDF under 10 MB on a Mac, open it in Preview, choose File > Export, and apply the “Reduce File Size” Quartz filter; for most image-heavy files that alone lands well under the limit. If it misses, or the pages come out too rough, shrink it to a named size instead with a tool that targets the number directly, and aim for 9 MB rather than 10 so the portal’s own arithmetic cannot trip you up.

Check what the portal is really measuring

Before compressing anything, be sure what “10 MB” means to the site you are uploading to. Finder reports sizes in decimal megabytes (1 MB is 1,000,000 bytes). Some upload systems count in binary (1 MB is 1,048,576 bytes), which is slightly more generous, and some check against a hard byte count that is slightly less generous than either. You will not know which until it rejects you.

The safe rule is to give yourself margin. Target 9 MB. A file at 9.9 MB in Finder can still bounce off a portal that enforces 10,000,000 bytes exactly, and every retry costs you another round of exporting.

To see an exact byte count on a Mac, select the file in Finder and press Command-I. The Size line shows both the rounded figure and the precise number of bytes in parentheses.

Work out what is taking the space

A text-only PDF of 20 pages is usually under 1 MB. If your file is 40 MB, it is carrying images, and the type of image decides the fix:

• Photos placed in a document (a report with pictures, a portfolio, a brochure). These compress well. Downsampling to screen resolution often cuts the file by 80 to 90 percent with no visible change on a laptop display.
• Scanned pages (a signed contract, ID documents, bank statements that came out of a scanner). Every page is a photograph of paper, typically in color at 300 dpi or more. These are the files that most often hit portal limits, and they have a dedicated walkthrough: how to compress a scanned PDF on a Mac.
• Slides exported to PDF. Presentations export with a full-resolution image per slide plus any embedded photos. Re-exporting from Keynote or PowerPoint with lower image quality usually beats compressing afterward. See how to make a PowerPoint or Word file smaller on a Mac.

A quick diagnostic: divide the size by the page count. Under 100 KB per page is text with light graphics. Around 500 KB per page is photos or a modest scan. Several MB per page means high-resolution scans or print-ready artwork, and those need the strongest settings.

Method 1: Preview’s built-in filter

This takes under a minute and solves the problem more often than not.

1. Open the PDF in Preview.
2. Choose File > Export.
3. Keep Format as PDF.
4. From the Quartz Filter menu, choose Reduce File Size.
5. Change the file name so the original stays intact, and click Save.
6. Select the new file in Finder and press Command-I to confirm the size.

The filter downsamples images aggressively and applies heavy JPEG compression. For a 30 MB file of phone photos it will often produce something around 2 to 4 MB. For a dense scan it can go either way: sometimes it cuts the file by three quarters, sometimes the scan’s pages become hard to read. Open the result and zoom to 100 percent on a page with the smallest text before you upload it.

If you want a gentler version of this filter that keeps pictures presentable, the general guide to compressing a PDF on a Mac walks through duplicating the preset in ColorSync Utility with your own resolution and quality numbers.

Method 2: shrink it to the number

Exporting, checking, adjusting and exporting again is fine for one file. It stops being fine when you have a tax return, three statements and a scanned passport to upload before a deadline, each with its own limit.

Manatee has a Shrink mode that works from the target backward. Drop the PDF onto the window, type 9 in the size field, and it searches for the strongest image quality that still fits under 9 MB, then writes a new copy beside the original. The original is never altered. The processing happens entirely on your Mac, which matters when the documents are the kind you upload to portals: ID, financials, medical records. Nothing is sent anywhere, and the app needs no account. Every feature is free for the first 24 hours.

What it will not do: Manatee cannot remove pages, rewrite text, or split a document, and it cannot make a PDF smaller than its text and structure allow. If a 200-page scanned file simply has too many pages to land under 10 MB at readable quality, the answer is splitting, below.

Method 3: split the file

Many portals allow multiple attachments, or a separate upload slot per document. If compression alone cannot get there without wrecking legibility, divide the PDF into parts that each fit.

1. Open the PDF in Preview and show the sidebar (View > Thumbnails).
2. Click the first page of the section you want to break out, then Shift-click the last page.
3. Drag the selected thumbnails onto the desktop. Preview creates a new PDF containing just those pages.
4. Repeat for each part, then compress each part if needed.

Alternatively, use File > Print, set the page range under Pages, and choose Save as PDF from the PDF menu at the bottom-left of the print dialog. This route also re-renders the pages, which occasionally shrinks a strangely bloated file on its own.

Name the parts clearly (“Statement_part1of3.pdf”) so whoever opens them on the other end can follow along.

Merging several documents without overshooting

The opposite problem is just as common: the portal wants one PDF, and you have five. Combine them in Preview by opening the first one, showing thumbnails, and dragging the other PDF files from Finder into the sidebar. Drag the pages into the order you want and choose File > Save.

Compress the individual files before merging, not after. A merged PDF made from already-compressed parts will land under the limit predictably, while compressing one large merged file applies the same blunt settings to a crisp text page and a murky scan alike.

One last check before you upload: if the documents include anything personal, be aware that compression does not remove the author name, creating application or modification dates embedded in the file. That is a separate step if it matters to you.

Questions

The portal still says the file is too large even though Finder shows 9.8 MB. Why?

The portal is probably counting bytes against a strict limit, or measuring something other than the file on disk (some add encoding overhead during upload). Aim for 9 MB or lower and the problem goes away.

Will compressing the PDF make it unreadable for the person reviewing it?

Not if you check it. After compressing, open the result and zoom to 100 percent on the page with the smallest text. If names, numbers and signatures are clear on screen, they will be clear to the reviewer. If they are not, use a gentler setting and split the file instead.

Can I get a PDF under 10 MB without changing the image quality at all?

Only if the bulk is not images: a bloated file from a design app can sometimes be fixed by re-exporting without layers or editing capability, and that changes nothing visible. If the file is big because of photos or scans, some reduction in resolution is the only lever there is.