You can use Preview to study or for research with its simple highlighting tool. You can highlight in several colors and see a list of all of the text you have marked. You can also add notes through the document.
A little-known use for the Mac Preview app is to import photos from an iPhone, camera or SD card. This functionality is similar to using Image Capture, but coupled with Preview's ability to view and edit the photos as well. It doesn't work perfectly with iCloud Photo Library, since it is hard to know which photos are actually on your iPhone at any given time.
In Preview you can open multiple images at the same time and export them all at once in a new format. You can also resize all of the open images at once, forcing them images to scale to a specific percentage or fit into a specific size. You can also do some other things in batches, such as rotations.
You can use the pen tool to draw on image and PDFs in Preview. Rough shapes and lines will be converted to smooth and perfect shapes and lines, but you can always choose the freehand drawing instead. You can move, resize and change the properties of shapes after you draw them.
You can add a magnifying loupe to an image or PDF in Preview. These loupes can help you point out something in an image or enhance the effect of an image that you plan to share. You can also use loupes to annotate images and PDFs during collaborations.
You can sign PDF documents in the Preview app and in Mail. You save your signature using either the trackpad or your Mac's camera. You can then insert that signature in any spot in the PDF. It then becomes a permanent part of that PDF just as if you had printed out the document, signed it, and then scanned it back in. You can do the same in Mail, but only the copy sent will contain the signature.
Learn how to create a transparent graphic that you can then overlay in iMovie to point out an area of interest. You can then have that graphic move around on the video to follow a subject. You can use this to highlight something in the video, or hide a face or some other element.
You can annotate PDF documents using Preview. You can use a variety of tools such as highlighting, notes, adding g arrows, shapes and text. Annotations can then be edited or removed by others using Preview or Adobe Reader. You can also mark up images, though you cannot edit them after saving.
You can use Preview's editing tools to cut out a piece of an image. You can then paste that image in another picture. You can also copy a portion of an image, adjust the color in the rest of the image, and then paste the original segment back to make a part of your image stand out.
You can use Preview to edit images without needing to take them into iPhoto or an app like Photoshop. You can adjust the colors in an image, crop it, rotate it and even copy and paste portions of the image from one image to another. You can also resize and then export an image, which is something you may want to do before sharing a photo online.
You can use Preview to easily merge two PDF files, or bring pages from one into the other. You can also create new documents from pages selected from another PDF. You can even bring images into PDFs as new pages.
You don't always need to print an entire document. Sometimes only a portion of a single page is all that is needed. By using OS X's ability to print to a PDF that opens in Preview, and some quick keyboard shortcuts, you can select and print only a small portion of a page, therefore saving paper and ink. This tip works for web pages, documents, or anything that can be printed.
You can perform some basic and fun image editing using only the Preview app that comes with your Mac. You can cut out a part of one image and paste it into another. You can also crop and resize an image before exporting it to share it.
Learn how to use Preview in Mountain Lion to merge two or more PDF documents into one file. You can also re-arrange the pages in a PDF document or delete pages.
With Preview in Lion, you can record your signature in Preview and then apply it to PDF files and other documents. Use your Mac's camera to take a picture of your signature. Add a variety of signatures and other stamps to your Preview preferences and use them with the annotations feature.
Learn how to use Snow Leopard's Preview application to cut out backgrounds or objects in images and photos. Preview has a standard Lasso Selection tool, a Smart Lasso tool and an Instant Alpha tool that can be used for this purpose. You can use these semi-transparent images on top of other images, in documents or in iMovie.
You can use Preview in Snow Leopard to merge documents and pages within documents. It works a little differently than it did in Leopard because you can have multiple documents in the sidebar which can confuse things.
You can go even further with Print As PDF by printing into Preview and then saving the preview document. You can reduce the file size or apply any number of Quartz filters. You can even make your own filter. You can also save as an encrypted PDF.
Preview was updated for Snow Leopard to include some powerful annotation features. You can now mark up documents and images with lines, notes, highlights and links.