- Bookmark a page by appending "#page=n" to the book's URL. E.g. "http://blah.pdf#page=23". The number, n, seems to be the page number from the first page (usually displayed as "n of m"). Useful for documents without a table of contents.
- Set the zoom level by appending "zoom=x" to the document's URL. E.g. "http://blah.pdf#zoom=150". The number is a percentage, so "150" = "150%".
- Combine the extensions using "&". E.g. "http://blah.pdf#page=23&zoom=150".
The parameters as the same as the command line switches for Adobe Acrobat (see below) but I was only interested page number and zoom: Parameters for Opening PDF Files