April 7, 2014 578

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.