Get a Mac PDF under the size limit

A rental scan, a MacBook Air and a 2 MB upload box

Tomas rents a flat in Brno and the agency's portal closes applications on Friday at 5 pm. The portal wants one PDF with his ID, three payslips and a bank statement, at most 2 MB. He scanned everything with his phone into a 14-page file called rental-pack-scan.pdf, and Finder says it weighs 18.6 MB. His MacBook Air has Safari, Preview and plenty of battery, but no PDF software beyond what Apple ships.

He does not need any. The fastest route on a Mac is a browser tab: open the tool, type 2 MB as the target and download a file that fits. Preview can shrink the file too, without internet, but it gives no size target and often shrinks images harder than needed. The next section compares the two routes so he can pick in ten seconds.

Preview or the browser: pick your route in ten seconds

Both routes keep the file on the Mac. They differ in control: one asks for the number you need, the other guesses for you.

When the recipient named a cap, the browser route wins every time, because only it aims at that number. Preview's filter is a single strength: on some files it lands far above the cap and the upload still fails, on others it smooths photos into wax. Use it when the network is down or when any smaller file will do. The general shrinking guide explains what each method drops inside the file.

Shrinking the file in Safari

1. Open Compress PDF in Safari. Chrome on the Mac works the same way.
2. Press Choose a PDF and pick the file in the Finder dialog, or drag it from a Finder window onto the page.
3. Tap the 2 MB preset, or type the exact cap from the portal into the target field and check the unit beside it, KB or MB. For a strict form, type a touch less, such as 1.9 MB.
4. Press Compress and keep the tab in front until it finishes. A 14-page scan takes seconds on a modern MacBook.
5. Read the verdict: new size, how much was saved and which technique did the most work. Glance at the preview beside the original and zoom into a page with small print.
6. Press Download PDF. The file keeps your name with "-compressed" added, so Tomas gets rental-pack-scan-compressed.pdf next to his original.

The tab counts a kilobyte as 1,024 bytes while some portals count a flat 1,000, which makes their cap sit about 2% lower. If a file that looks like it fits still bounces, lower the target a little and run it once more.

Where Safari drops the finished file

Safari saves downloads to the Downloads folder unless the location was changed in its settings, so the compressed copy lands in Finder under Downloads. Chrome on a Mac does the same. If the portal's file picker opens somewhere else, choose Downloads in its sidebar.

Before uploading, check the size yourself: select the file in Finder and press Command+I to open the info panel, which shows the exact byte count. Confirm the name carries "-compressed" so you do not attach the 18.6 MB original by accident, then open the file once in Preview and skim every page.

What goes wrong on a Mac, and the fix

• Exporting from Preview twice. Running Reduce File Size on its own output re-encodes already softened images. Keep the original and shrink that once, in one pass.
• Typing the size you have, not the size you need. The target field asks for the ceiling from the portal, not the current weight in Finder. Read the form first.
• Mixing up KB and MB. A target of 2 KB instead of 2 MB asks for something no scan can reach. The unit sits right beside the number, check it.
• Compressing a locked file. A PDF that asks for a password just to open resists the rebuild tricks compression relies on. Unlock it first, then compress the unlocked copy.
• Closing the lid mid-run. A Mac that sleeps pauses the tab. Keep the lid open and Safari in front until the download appears.
• Sending without opening. Every candidate is reopened and checked before download, but your eyes are the last check. Skim the download in Preview before attaching it.

When to let Preview do it instead

Use Preview when there is no connection: a train, a plane, a cottage with dead wifi. Open the PDF in Preview, open the Export dialog from the File menu, pick the Reduce File Size filter and save a copy. Check the copy in Finder afterwards, because the filter never promises a number.

Skip shrinking entirely when the file heads for professional print. Press workflows measure resolution and color, and a screen-tuned file prints soft, so send the original to the printer. If a contract forbids opening the document outside approved software, keep it in the approved app and ask IT for the sanctioned route. And when the file must shrink tenfold but every photo must stay crisp, no setting squares that circle: split the document into parts that each fit, or ask whether a shared folder link works instead.