Hook integration scripts v.150 now available - Interapp Deep Linking with Skim app


Whether they are working by themselves or collaborating, academics, lawyers, software developers, researchers, administrators and/or others who work extensively with PDFs often need to be able to reference specific page numbers in PDF files — and locations on those pages.

As an academic, software lead, author and manager myself, I’ve needed deep-PDF linking functionality for many years.


Version 150 of Hook’s app-integration scripts is now available. These scripts enable users to copy deep PDF links using the free PDF reader, Skim, which is available on Sourceforge.io and open them in any compatible PDF app.

Please see Using Hook with Skim PDF Reader app for more information.

Switching between PDF readers, and compatibility of deep PDF links

The deep-linking functionality introduced in this update leverages the same Hook 2.2 functionality that enables Hook’s Deep Linking with PDFPenPro.

Hook’s deep PDF linking is designed with the same standard-leveraging principles and philosophy as Hook’s email links. (See Openness). Where Hook’s email URLs (hook://email/<ID>) utilize RFC 5322 compliant email identifiers, Hook’s deep PDF URLs (hook://file//<...>p=<page-number>&s<starting-point>&e=<end-point>) use coordinate information specified in PDF specifications.

You already know that when you use Copy Link with a truly linkable email app (like MailMate, Airmail and Apple Mail), you get a URL that can be opened with another email app (by yourself or a different person).

The same principle applies to Hook’s deep PDF links. You can create a deep link in one PDF app and open it in another. You can copy a deep PDF link in one app (say Skim) and open said deep links in another app (say PDFpenPro).

Preview and Adobe Reader lack an API for deep linking. If your favorite PDF app lacks a deep linking API, see Contacting Developers of Other Apps and Information for Developers – Hook.

Even if the target app does not support deep linking, however, you’ll at least be able to use the link produced by Hook to open the entire PDF.

Benefits of deep PDF links

Elsewhere, we’ve described some of the benefits that Hook’s deep PDF links provide. They inherit properties of the hook://file// scheme. For example, you can move the PDF files around, rename them and even share them.

We’ll write more about deep PDF linking soon, and publish some screencasts about it too.


Please feel free to share this information with other professionals / associations who could benefit from deep linking. Perhaps the best place to start is when you review your colleagues’ PDFs.

The free Lite mode of Hook enables your colleagues to utilize (“consume”) Hook’s links, including PDF links. (They can even create email links with Hook Lite).

Discussed on twitter:

“Hook now supports deep PDF linking with Skim as well as PDFpenPro” / Twitter

How to get the updated integration

Hook’s automatic software update (if enabled) automatically updates Hook’s integration scripts without you needing to relaunch Hook. Using Hook’s Check for App Updates and Update Scripts command also updates the scripts, without you needing to relaunch Hook.

We also bundle Hook’s integration scripts with the Hook installer itself, of course. We update Hook’s integration server more frequently than the app itself.

Updated 2021-01-07 22:36 PT: fixed minor typos.

Thanks Luc. I’m trying to link to Skim (deep links), but Skim doesn’t even open.

I’m using Obsidian as source, and if I use Preview as default app, it opens, albeit only the file itself. The link is a deep link like so:


But the moment I select Skim as default app for PDF, it doesn’t open when clicking the link.

Thanks for help,


could you please share here or PM a deep link in question? Best to escape it between ticks, because discourse chews up app links

Example: [Mental Perturbance.pdf](hook://file/vHFu89DxS?p=MjAyMS0wMyBEZWVwIExpbmtpbmcgLSBEZWVwIFJlYWRpbmcgUERGcGVuUHJvIEJsb2cgUG9zdCAtIFNtaWxlL1Jlc291cmNlcw==&n=Mental%20Perturbance.pdf#p=21&x=0&y=0&s=1857&e=2038) is a deep link I got from Skim, that opens on page 21 of that file , which is from a researchgate paper of mine, named Mental Perturbance.pdf. If you download that PDF and call it Mental Perturbance.pdf , the link above should work for you too.

I recently created a very extensive example, published here:
How Deep Links Can Help You Master a Document – CogZest, and in a more accessible form on Smile’s PDFpen website (linked from latter web page).

I take it Hook’s integration scripts are up to date on your Mac…