How can I programmatically open a pdf at a certain point?

Question

I've seen a few apps load up pdf files as the documentation but at a certain point within the pdf file. How were they doing this?

Answer 1

Setting a page parameter or named destination on the URL. See the docs on open parameters:

Specifying PDF Open Parameters in a URL

You can specify multiple PDF Open parameters in a single URL. Each parameter is separated from the others with either an ampersand (&) or a pound (#) character. Actions are processed and executed from left to right as they appear on the URL command line. Because all specified actions are executed, it is possible that later actions will override the effects of previous actions, so it is important to be aware of the order. For example, page actions should appear before zoom actions. Commands are not case sensitive (except for the value of a named destination). There can be no spaces in the URL line.

URL Examples

http://example.org/doc.pdf#nameddest=Chapter6
http://example.org/doc.pdf#page=3
http://example.org/doc.pdf#page=3&zoom=200,250,100
http://example.org/doc.pdf#zoom=50
http://example.org/doc.pdf#page=72&view=fitH,100
http://example.org/doc.pdf#view=fitb&nameddest=Chapter3
http://example.org/doc.pdf#pagemode=none
http://example.org/doc.pdf#pagemode=bookmarks&page=2
http://example.org/doc.pdf#page=3&pagemode=thumbs
http://example.org/doc.pdf#collab=DAVFDF@http://review_server/Collab/user1
http://example.org/doc.pdf#page=1&comment=452fde0e-fd22-457c-84aa-2cf5bed5a349
http://example.org/doc.pdf#fdf=http://example.org/doc.fdf