PDF tools for Mac: what Preview does, and what it cannot

What Preview already does on a Mac

Preview is the app that opens PDFs on every Mac. Apple's Preview guide covers combining PDFs, adding, deleting and moving pages, signing, and reducing the size of a PDF. For most everyday jobs you need nothing else.

Recent versions of macOS also let you select text in a scanned PDF in Preview, which covers casual copying without a separate OCR tool.

• Combine PDFs: open one PDF, show the thumbnail sidebar, and drag the pages or the second file into it, or use Edit, Insert, Page from File.
• Reorder and delete pages: drag a thumbnail to a new position, or select it and press Delete.
• Pull pages out: select thumbnails and drag them to the Desktop to get a new PDF.
• Sign and fill in: use Markup to add text, shapes and a signature.
• Password: choose the Encrypt option when you export the file.

How to merge PDFs on a Mac with Preview

1. Open the first PDF in Preview and choose View, then Thumbnails.
2. Drag the second PDF from Finder into the thumbnail sidebar, below the page you want it to follow.
3. Drag thumbnails up or down until the order is right.
4. Choose File, then Export as PDF, and save the result under a new name so the originals stay untouched.

Check the page count before you send it. If you do this weekly, Preview is quicker than any website.

How to compress a PDF for email on a Mac

Preview has one built-in way to shrink a PDF: File, Export, then the Quartz Filter menu, then Reduce File Size. It applies a single fixed setting. It can shrink a scan a lot, and some people find it makes images and text look soft, so open the result and look at it before you send it.

It will not aim for a number. If the mail system or a portal rejects anything over 2 MB, you are left repeating the export and checking the size by hand.

For a limit you can name, open Compress PDF to an exact size, choose the target and download the result. Size pages for common limits include 1 MB, 5 MB and 10 MB. The tool reports the size it reached, and it keeps your original if a compressed copy would come out larger.

Mail Drop: when you do not need to compress at all

Apple Mail has a feature called Mail Drop. When a message is larger than your email provider allows, Mail offers to send the attachments with Mail Drop instead. The recipient gets a download link, not the file, and Apple says the attachments do not count against your iCloud storage and can be up to 5 GB per message, with links that expire after 30 days.

That solves sending a big file from Mail. It does not help when a web form, a job portal or a recipient on a strict system needs a small attachment, which is the case compression is for.

When a browser tool is the better answer on a Mac

• The file must be under a specific size: Compress PDF to an exact size.
• You want to keep selectable text while shrinking the file: Compress PDF has a mode that only recompresses the images.
• You want to remove a password you know from a file for good: Unlock PDF.
• You are on a Mac you do not control, such as a library or office machine where you cannot change settings: a browser tool needs no installation.

Limits on a Mac

The browser tools work in the tab, so a very large scan is limited by the memory your Mac has free, not by a cap we set. Compression to a target size works best on scans and photo PDFs. A mostly-text PDF barely shrinks, because there is little to remove. Preview and these tools can add a simple electronic signature image. Neither produces a qualified or certified digital signature.