How to save copy of a PDF with a different fingerprint

How to save copy of a PDF with a different fingerprint2020-04-29T12:03:52-07:00
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The ability to assign the same PDF to small groups of students, rather than having the whole class annotate together, is a feature we’re in the process of developing for our LMS app. In the meantime, you can follow the directions below as a workaround. 

What is a PDF fingerprint?

PDFs contain a digital signature that allows you to tell different documents apart. Hypothesis started using these fingerprints in 2016 to make sure that multiple users who all download the same copy of a PDF could see each others’ notes. In the LMS app, this means uploading the same PDF multiple times in a course site will result in annotations syncing across those copies.

This article helps you accomplish the opposite; you can make multiple copies of the same PDF with different fingerprints. Once you’ve done this, an annotation made in one copy will not appear in another. You can then use your LMS’ built-in groups feature to make each fingerprinted copy available to a small group of students. 

How do I make two copies of a PDF that have different fingerprints?

Don’t just copy the PDF…

When you copy a PDF (for example, in a file manager), you also copy the fingerprint, meaning that Hypothesis will view your copy as if it were the original document. 

…instead, print the PDF again

To make sure the new PDF has a different fingerprint, you need to print a new version of the document. To do this in Chrome:

  1. Right click on the PDF and rename it using a distinguishing name, like “Group 1 – [AssignmentName]”.

  2. Right click on the PDF in your file manager and choose “Open with” and “Chrome”.
    Opening a file in file manager with Chrome
  3. At the top of the PDF window in Chrome, select the Print icon.
    PDF Print icon in Chrome

  4. Choose “Print to PDF” as your destination and give the new PDF a name like “Group 2 – [AssignmentName]”.
    Two versions of a PDF in a file manager

As long as each PDF has a different fingerprint, users in one PDF will not see the annotations of users in the other PDFs.


How I do I check and make sure my PDFs have different fingerprints?

See our related Knowledge Base article here.


How do I create more than two unique fingerprints?

At this time, there does not seem to be a consistent method across all platforms for creating more than two unique fingerprints for a given PDF. For Mac users, you might try printing to a PDF within Mac Preview.

If you’re trying to create more than two unique fingerprints for the purpose of small group readings for education, our LMS app will have this functionality soon!

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