Open two instances of the same PDF in Mac OS X Preview

Question

I have a file example.pdf, where the key to exercises in the top part of the document are posted at the end. Hence, I want to open two instances of this file, so that I can put the window with the answers next to the one with exercises.

A possible solution is of course to cp example.pdf example_copy.pdf, but I wonder if this be done without copying and renaming the file?

Answer 1

Open a document in a new instance of its associated application like this:

open -n path/to/file.pdf

Open also allows you to specify the application for the file, but if Preview is your default PDF viewer, you don't need to.

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Another option is to bookmark relevant pages of the document, and jump between them by using the Back and Forward commands (Cmd-[ and Cmd-]).

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The command above can be wrapped in a Service that can be assigned a keyboard shortcut in System Preferences » Keyboard using Automator:

Unfortunately, Preview cannot be scripted, and this Service cannot be launched from within Preview when viewing the document. You can, however, use it in Finder, either via its Finder » Services menu, or the context-menu of any file.

Answer 2

Rather than open a whole new instance of Preview (which would then prevent you from toggling which document is in front with command+`), the easiest thing I can think to do for this is copy the pages you want in a new window and use "New from Clipboard" in the file menu. No command line required:

1. Open the document
2. Select desired pages from sidebar, or use command+a for select all.
3. command+c followed by command+n — copy pages from clipboard and create a new document containing those pages.