Deep PDF Links Take You Right Where You Need to Focus

2021-05-08 Update: Hook now also provides deep linking for Adobe Reader and Adobe Acrobat. See linkable apps. However, Hook aside, we recommend PDFpenPro and Skim for reading in depth (“delving”).

PDFs are used to capture some of the most important, and best, information we all work with. If you’re a knowledge worker, an attorney, an academic, or a student, odds are you spend a lot of time reading PDF files. However, PDFs can be quite long. Anything that can radically improve your cognitive processing of PDFs can make a big difference in the quality and quantity of the work you produce. So can anything that makes it easier to access and use key information from PDFs. Deep PDF-linking is a case in point.

The thing about PDFs is that they’re reference material. So you need to be able to refer to them from outside of the PDF, such as in your notes, other documents, and emails. Before Hook, however, it was challenging to adequately refer to (link to) entire PDF files on your Mac, let alone to specific locations in PDFs, known as “deep PDF-linking”. Sure, there are aliases; but they can’t be embedded in files and they’re brittle. File (file://) links are even more brittle. App-specific PDF links (when available) bind you to a particular PDF reader.

Hook changes all of that. With Hook, you can robustly link to PDF documents, and by using Hook with PDFPenPro or the free Skim PDF reader (more PDF software coming soon!), you can also link to specific locations within PDFs.

Once you’ve used Hook to copy a deep PDF link, you can paste it anywhere, such as in

This means that, with the click of that pasted link, you can instantly access the exact location in a PDF file that is relevant to you. That is to say, you can link to specific text in a PDF, image coordinates, in a PDF, or page.

So for example, if you’re a lawyer who has detected an important contradiction in the other side’s testimony, you can add an item in your todo list to follow up on it. Click on the link days or weeks later, and you’re back in context. You can even send your colleague or client a link to that specific location in the document.

If you’re an academic, and you’ve found an important flaw in a grant proposal or paper, you can also add this to your notes and task list. You can even email your colleagues about it.

It does not stop there. With Hook, you can also bidirectionally link your PDF to other resources, i.e., “hook them together”.

How to copy deep PDF links with Hook

If you have selected something in a PDF opened with PDFPenPro or Skim when you invoke Copy Link or Copy Markdown Link, then Hook will copy a “deep link” to the specific location of the selection! This is super-handy for anyone who is working intensely with PDFs.

  1. In Skim or PDFPenPro, select the text or image to which you want to create a link.
  2. Bring up Hook using a keyboard shortcut (⇧⌘SPACE by default) or the Hook menu bar icon.
  3. Click Hook’s Copy Link button (or use ⌘C, or Copy Markdown Link).
  4. Paste the link wherever you want to directly link to the selection.

When you click the link, Hook opens the file and jumps to the specific section of the PDF, provided your default PDF reader supports PDF deep linking. (As of January, 2021, Skim and PDFpenPro support this functionality).

Share deep links to PDFs with others!

Before Hook, there was no easy way to refer to PDFs shared in Dropbox or iCloud. Hook solves this problem. Use the Copy Link (or Copy Markdown Link) command on a PDF or a selection of the PDF (in Skim or PDFpenPro), then paste the link into a document or email. Send it to anyone with access to the PDF. If they have Hook (even if they use its free Lite mode), the PDF link will open the file. If they also have PDFpenPro or Skim (which is free) set as their default PDF reader, deep links will open at the exact location in the PDF.

Instead of manually scrolling to the location in a (potentially very long) PDF, all they need to do is click on the Hook link.

Try it, you and your recipients will be amazed at the time (and communication) savings!

Delivering on Douglas Englebart’s hyperlink vision

One of the great pioneers of information technology, Douglas Englebart, wrote decades ago about the importance of in file addressability and bidirectional linking. Hook helps achieve that vision, and then some.

In the book, The Future of Text, co-founder of CogSci Apps Corp and of CogZest, Luc P. Beaudoin, recently published A Manifesto for User and Automation Interfaces for Hyperlinking, which explains the importance of Englebart’s hyperlinking vision and what is required, in a modern context, to achieve it.

We are leading an initiative, with several Mac software developers and thought leaders, to publish an accessible manifesto based on Beaudoin’s manifesto chapter. Interested parties may contact us on that page.

Find out more about deep PDF-linking

Hook deep linking is compatible with apps that are truly deep linkable. This currently includes PDFpenPro and Skim. For more information, check out

Hook and Curio’s Deep PDF-Linking

Hook is also compatible with Curio, the user-friendly note-taking, brainstorming and mind-mapping app for the Mac that contains a PDF viewer with deep PDF-linking. See

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