How do you make a PDF smaller on a Mac?
Open the PDF in Preview, choose File → Export, pick Reduce File Size from the Quartz Filter menu and save. Apple warns that the result may be lower quality than the original, and that is the catch: the filter applies one fixed setting to every picture, with no size to aim for. Some files shrink a lot and come out soft; others barely change.
For control, open Compress PDF in Safari or Chrome instead. Type the size you need — 2 MB, 500 KB — and it finds the lightest compression that reaches it, with a before-and-after to check.
How do you make a PDF smaller on an iPhone or iPad?
The Shortcuts app has an action called Optimize File Size of PDF. Build a shortcut around it — take a file from Files, optimize it, save it back — and you can run it from the share sheet. It is gentle: high-resolution pictures stay high-resolution, so a photographed or scanned document often shrinks only a little.
In Safari, Compress PDF does the same job as on a computer: choose the file from Files, type the size, and save the result back to Files. Nothing is uploaded, which matters for the IDs and statements people most often need to shrink on a phone.
How do you make a PDF smaller on Windows?
Windows has no PDF compressor. Re-printing a file through Microsoft Print to PDF produces a new PDF, but there is no size or quality setting, links and bookmarks are lost on the way, and the result is sometimes bigger than the original.
Open Compress PDF in Edge or Chrome instead. It runs on the PC itself, so a 200 MB scan doesn’t have to go up a slow connection and come back down.
How do you make a PDF smaller on Android?
Android has no built-in way to compress a PDF you already have. Open Compress PDF in Chrome, pick the file from Downloads or Files, type the size and save. On an older phone a large scan takes longer than on a laptop, but it gets there — and the file never leaves the phone.
Which settings matter, whatever the device?
Pictures are where the megabytes are. Text and vector drawings are already compact, so a 40-page typed report may be 300 KB while a 4-page scan is 12 MB. Compression works on the pictures; if a file is mostly text, there is little to take out.
Aim under the limit, not at it. Email attachments grow by about a third in transit, so a 25 MB email limit means a file of about 18 MB, and a form that says 2 MB may mean 2,000,000 or 2,097,152 bytes. Check the final number with PDF Size Checker, which also tells you whether a typical upload form will accept the file.
Why does the same PDF shrink differently on each device?
Because each built-in option uses its own fixed recipe: Preview’s filter is aggressive, the Shortcuts action is mild, and Windows’ print route isn’t compression at all. A browser tool runs the same engine everywhere, so the same file and the same target give the same result on a Mac, a PC and a phone — only the time it takes changes.