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Apple’s Preview: Still not safe for work

Preview - Not Safe For Work

I love Apple products. My desktop is a Mac Mini, my road-warrior is a MacBook Pro and I upgrade my iPhone every other version. My iPad 1 still works reasonably well; I never guessed its batteries would have lasted this long.

But as someone intimately involved in developing international standards for software I am appalled by some of Apple’s choices when it comes to supporting PDF in Preview, the default PDF viewer on Mac OS.

It’s OK that Apple only supports a few of PDF’s features. What’s really not OK is that Preview in many cases damages the PDF documents it saves with zero warning to the user.

Now, of course there’s no law compelling support for ISO 32000-1, the ISO standard for PDF since 2008. That said, destroying existing features without any warning to the user is a real no-no. See the first 10 problems I noticed, below.

Take one example: PDF/A (archive)

This standard (formal name: ISO 19005) was first published in 2005. The format has been adopted by governments and companies worldwide. The PDF/A flag is extremely easy to detect and remove when necessary.

Preview does not support PDF/A, and thus cannot re-save a PDF/A file it encounters as another PDF/A file. No problem so far – that’s a perfectly legitimate limitation. But Preview leaves the PDF/A flag in-place when saving the file, as if the document still complies with the standard!

It’s simply not OK to both trash PDF/A files and subvert the PDF/A metadata flag, not even for Apple. To do so with no warning to the user at all is reprehensible.

Yes, these are strong words…

Even more so because my role is far more often to smooth over differences between software vendors, and help them find ways to cooperate. First and foremost, however, I’m an advocate for the consumer, who (for obvious reasons) has to trust that responsible software companies will do the right thing. Secondarily, I’m an advocate for PDF itself, the embodiment (in principle, and usually, in fact) of reliability and interoperability in pages and documents.

It’s not for nothing that the National Archives and Records Administration’s latest guidance on archiving to US federal agencies requires “valid” files.

10 examples of how Preview fails to meet the standard, with dire consequences

The following table displays a few of the more obvious ways in which Preview fails to meet current ISO standards for PDF, not to mention standards of common courtesy to valued customers. In each case Apple has an easy way out if they prefer not to support the feature: warn the user.

FailureCategorySeverityBehavior in 10.9.2Correct action
No support for digital signaturesViewingLoss of access, misrepresentationDigital signatures are not acknowledged If Apple chooses not to support Digital Signatures Preview should warn the user that the PDF is digitally signed.
Destroys digital signaturesSavingData loss without warning, misrepresentationThe signature is destroyed; an image is substituted If Apple chooses not to support Digital Signatures then Preview should refuse to edit a signed file or else warn that the signature will be lost. Pretending the signature is still intact is a gross misrepresentation.
Ignores tagged PDFViewingInaccessibleVoiceOver does not use Tagged PDF and thus cannot follow the logical structure of the documentIf Apple chooses not to support Tagged PDF for accessibility that is their prerogative, but if so cannot claim to support PDF with their accessibility software
Destroys tagged PDFSavingData loss without warningExisting tags are deletedIf Apple chooses not to support Tagged PDF then Preview should either: (1) Leave existing tags intact, or (2) Warn that the tags will be lost on save
Ignores PDF/AViewingMisrepresentationUsers get no indication of PDF/A statusIf Apple chooses not to support PDF/A they could still advise the user that the file claims PDF/A compliance
Destroys PDF/ASavingData loss without warning, misrepresentationPDF/A status is compromised, but the PDF/A flag remains, misleading the user!If Apple chooses not to support PDF/A the very least they can do is remove the PDF/A flag when saving the file
Ignores attachmentsViewingLoss of accessPreview does not expose files attached to a PDF If Apple chooses not to support the attached files feature of PDF they should warn the user on opening that "this file contains attachments which are not available in Preview".
Destroys attachmentsSavingData loss without warningAttached files are deleted If Apple chooses not to support the attached files feature of PDF the very least they can do is warn the user before saving, or better, simply leave the attachment alone!
Poor support for standard PDF encryptionViewingLoss of access, misrepresentationFile cannot be opened, even with the correct password. The user is incorrectly advised that their password is invalidIf Apple chooses not to support standard PDF encryption they should tell the user the facts, not erroneously report an “invalid password”
Destroys OCGsSavingData loss without warningOCGs (a.k.a. “Layers”) are flattened into a single layer If Apple chooses not to support OCGs they should warn the user before flattening the file!

Note: The above opinions are mine alone. I am not speaking as Project Leader of ISO 32000, nor as Vice Chairman of the PDF Association. The facts, however, are the facts.


  1. April 7, 2014 at 13:33

    We are seeing more and more ‘interesting’ PDFs as more people use Quartz to create them 🙁

  2. July 22, 2014 at 10:56

    I hate Preview with a white-hot passion that can barely be contained by 6 inches of lead. The Mac OS is set up to use Preview to open JPEGs, PDFs, TIFFs, and PSDs; you have to disable that insistent behavior. But perhaps its most nefarious capability is the ability to strip security off PDFs when they’re resaved by Preview. Admittedly, that feature has saved my bacon once or twice, but I have used it only for Good, never for Ev-yil.

  3. July 30, 2014 at 19:36


    What, no forms? Both viewing and saving problems are rampant with Preview. It corrupts forms in more ways than I care to type out, though I do have add that all scripting is removed. The take-away message it should be avoided at all costs for PDF forms.

    If you can believe it, Microsoft Reader is even worse with respect to forms as it corrupts the data.

  4. July 31, 2014 at 16:29

    Thanks, George. I know Preview’s poor with forms but I’d not yet catalogued the ways. There are many other shameful things Preview does / doesn’t do with PDF. Perhaps it’s time to expand the list in this article to 20 items… or maybe just pick “The Top 20″…

  5. December 11, 2014 at 06:04

    I have just found out that Preview has sabotaged maybe dozens of PDFs I had saved using it. The problem is the way Safari itself works is it loads a PDF internally so to save a copy my usual practice is to select ‘Open in preview’ then save it to a suitable location (usually my desktop at first). However what I have found is in doing this Preview changes the PDF and in some cases makes impossible to text search it. I think this is the worst fault it has and am going to have to look for an alternative reader and workflow – how I wish there was a Foxit for Mac!

  6. December 24, 2014 at 15:05

    There is one more HUGE problem with Preview: It may save a corrupt file without you even knowing that the file was saved and therefore destroyed: Depending on certain settings in the operating system, Preview will automatically save a new version of the file when you just modify something in the file. You never actually hit the save button, you close the file and when you re-open the file, your original file is gone and replaced with your standard “Preview quality” PDF file.

    See here for information about how to disable that “feature”:

  7. Johannes Bols
    November 24, 2016 at 03:47

    You have hit the nail on the head! Twice in the last hour I’ve had to force quit preview (I’m working on a personal project, so I guess it’s just OK that preview destroys that, eh?). I have told my dad I would never, ever use Mac for a job or for remunerative projects because it wipes out precision, painstaking, hours of concentrated effort – with NO ability to reference said work. Even saving frequently does no good. It’s when I see the spinning beachball of death that I know the software writers for this programme are belly laughing on some beach, drinking rum punches and ruminating on the good life. Puh!

  8. Ben BW
    October 3, 2017 at 04:26

    It is such as shame, as Apple’s PDF framework could be superlative with a little more effort. Things like applying Quartz Filters could be amazingly useful if brought up to professional standard, but currently ColorSync Utility is fundamentally broken, and the underlying Quartz APIs lack many features.
    Apple’s Auto-save feature is very useful, but doesn’t fit with Preview, as users will often need to preserve original PDFs and images, even when making alterations. Preview deletes PDF pages with a touch of the delete button, without any warning, too.
    It is possible to turn off the auto-save in Preview, so that changes bring up the Save/Don’tSave dialog. But many users won’t know the need, or how to do that.
    It is possible to use Quartz in a professional workflow, but you have to know what you’re doing (and what Quartz is doing.)
    As always, if you want the bugs fixes or features changed, send feedback or report bugs to Apple.

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