The hidden powers of Mountain Lion's Preview


Preview is Apple's top-secret tool for viewing and manipulating PDF files, graphics, and more. The secret, however, isn't that it exists (look in your Applications folder) but that this seemly simple program harbors tons of advanced features. You can use Preview to annotate PDFs, delete or rearrange PDF pages, crop images, and more. Here's an overview of the recent additions to Preview that you may not know about.

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Take a closer look

When you're viewing a simple PDF--just a page or two--it's easy to scroll to see the content you need. But if you have a long document, it's more efficient to jump to the section you want instead of scrolling through dozens of pages. You can do that and more by clicking the View button to the left of Preview's toolbar. Here you'll see a pop-up menu listing these options:

  • Your viewing options. Content Only shows the pages of your PDF without displaying the sidebar. This is the default display. It's great when you need an uncluttered view of your document or image.
  • Thumbnails displays the sidebar, and in it, small thumbnail images of the pages of your PDF, or your collection of images. You can scroll through the sidebar quickly to find the page you want to see, and then click it to jump to that page. For most uses, you'll find that the Thumbnails view works best.
  • Table Of Contents displays text links for the PDF's table of contents. If you're reviewing a long document with a table of contents, this view can save you a lot of time hunting for material.
  • Highlights And Notes lists any highlights or annotations you have made. Click one to read it. See below for more about annotating PDFs.
  • Contact Sheet shows page thumbnails across the content section of Preview's window. This is especially useful when you're looking at a collection of images with Preview.

Note that the View menu also allows you to choose how Preview displays pages:

  • Continuous Scroll lets you scroll through a document while seeing page breaks.
  • Single Page shows only one page at a time.
  • Two Pages shows left and right pages together, so you can see layouts that stretch across a spread, say in a brochure or magazine.

Delete or rearrange PDF pages

If you're in Thumbnails view, you can easily delete or move pages within a PDF. To delete a page, click a thumbnail, and then press Delete. Save the document, and that page disappears.

To move a page, just click a thumbnail and drag it to the location in the sidebar where you want it to be. Save the document, and the page will take its new position.

Crop images

To crop an image in Preview, open the file and then choose Tools -> Rectangular Selection, if that isn't already checked. Hover your pointer over the file, and you'll see a crosshair cursor. Click and drag this cursor around the area to crop. When you stop, you'll see a marquee selection, which you can adjust from the sides and corners. When you have the exact crop you want, select Tools -> Crop (or press Command-K), and then save the file.

Try PDF annotation tricks

I wrote about annotating PDFs about a year ago, but Mountain Lion has made some interesting changes to this essential Preview feature. For instance, consider notes, perhaps the most commonly used annotation. To leave a note about something in a PDF, choose Tools -> Annotate -> Note. (Or reveal the Edit toolbar by selecting View -> Show Edit Toolbar, and then click the Note button.) Your cursor turns into a crosshair. Click where you want to write your note, and then type in the yellow box that appears.

The text of each note is hidden after you finish writing. Click any note (indicated by a yellow square on the PDF) to expand it and see your text in context again. You can also reveal note text by displaying the sidebar and choosing Highlights And Notes from the View menu on the toolbar. Instead of scrolling through a document to see notes, you can click a note in the sidebar, and Preview hops to that page.

You can also search your notes and highlights. Make sure the Highlights And Notes sidebar is visible, and then use Preview's search field to search for a string of text. The search will show results in that sidebar; if you want to go to the location of a hit, just click it. (If that sidebar is not visible, the search function will search only in your PDF's content.)

Depending on what you need to do with PDFs or images in Preview, it's worthwhile to explore the other tools in the Tools -> Annotate menu and on the Edit toolbar. Highlight Text (Command-Control-H) and Strike Through Text (Command-Control-S) can be particularly useful.

Sign a PDF

When you receive a PDF document by email from your bank, your school, or some other organization, it can be a puzzle to determine the best way to sign the file and return it to the sender. Before, you had to print out the document, sign it, scan it, and then send it. Now, you can save your signature and add it to any PDF.

To do this, choose Preview -> Preferences, click Signatures, and then click the plus sign (+) to create a signature. A Signature Capture window will appear, telling you to sign your name in black ink on white paper and then hold it up in front of your Mac's camera. Preview will flip the signature around so that it's in the right direction, and then, when you click Accept, will save it. You can see your signature in the Signature preferences, and if you need more than one signature--say, for your spouse or children--you can add more signatures.

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