HT202255: OS X Lion: About Auto Save and Versions

Learn about OS X Lion: About Auto Save and Versions
oliverj

Q: How are versions saved in Preview PDFs?

If you make a change to a PDF in Preview (such as deleting a page, which auto-saves with versioning), how does the versioning actually work when you share the document with others?  Can they access the previous versions?

Posted on Aug 28, 2015 1:07 PM

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Q: How are versions saved in Preview PDFs?

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  • by Kappy,

    Kappy Kappy Aug 28, 2015 1:19 PM in response to oliverj
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    Aug 28, 2015 1:19 PM in response to oliverj

    It doesn't. Other users only have the copy you provided to them. They have no access to your computer where the other versions will be stored. Sharing a document does not constitute sharing your computer unless that is what you want to do - give anyone complete access to your machine.

  • by oliverj,

    oliverj oliverj Aug 28, 2015 2:02 PM in response to Kappy
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    Aug 28, 2015 2:02 PM in response to Kappy

    I see, so the versioning is stored locally outside the source file itself?  How does cleaning up work, since I imagine that the versioning history could get quite large, especially with graphics-heavy PDFs.

     

    Could you point me to some tech docs that explain how their versioning mechanism works?  The docs on the Apple site are pretty bad in this respect.  Thx!

  • by Kappy,

    Kappy Kappy Aug 28, 2015 2:25 PM in response to oliverj
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    Aug 28, 2015 2:25 PM in response to oliverj

    The versions are stored in a separate folder, not within the document, unless that has changed. Versioning is done based on changes rather than saving whole copies which would use a lot of disk space unnecessarily.

     

    The only article I have is: OS X Lion- About Auto Save and Versions. You may find more by searching Google.

  • by oliverj,

    oliverj oliverj Aug 28, 2015 2:46 PM in response to Kappy
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    Aug 28, 2015 2:46 PM in response to Kappy

    Ya, that's the document I found and it's pretty poor.  I imagine there's some sort of Git-style versioning under the hood, but since PDF's often contain bitmap material, I'd be curious to see how the storing and cleanup actually works.  I guess I could dive into the developer docs, I was just hoping to find a bit more specifics without having to go into a deep dive.

     

    Additionally, security issues with local diff repositories is definitely a concern, so I'd like to understand if there is any encryption in the process.  This sort of system seems like it could be a security department's nightmare with persistent historical copies that are polluted throughout the system.

     

    Thx!

  • by Kappy,

    Kappy Kappy Aug 28, 2015 3:09 PM in response to oliverj
    Level 10 (271,328 points)
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    Aug 28, 2015 3:09 PM in response to oliverj

    Security is a different topic. If you use Mavericks or Yosemite you have full disk encryption. If a company is serious about security I can't imagine this being an issue.

  • by oliverj,

    oliverj oliverj Aug 28, 2015 3:24 PM in response to Kappy
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    Aug 28, 2015 3:24 PM in response to Kappy

    Ya, I agree, I'm more concerned with files potentially needing to be wiped in multiple places.  There's got to be documentation somewhere that covers the architecture...