Here’s a neat trick that can be used if you need to view the same images or PDFs repeatedly, or if you want to simply record your position within a long PDF document.
If there are images or PDFs that you view frequently, you can bookmark them within Preview, OS X’s image viewer. This works just like bookmarking websites within a web browser like Safari and uses the same keyboard shortcut–just load the image or PDF and hit Command + D. From then on, click the image or PDF’s entry on Preview’s Bookmarks menu to open it instantly.
If you bookmark a multipage PDF file, you’ll also bookmark the page you were reading at the time, so that clicking the bookmark in the future will return you to that page. This can be useful when reading ebooks.
Rather cleverly, even if you move the original file from one folder to another, Preview’s bookmark will still link to the file–even if it’s moved into the Trash!