This article originally appeared in TidBITS on 2017-04-03 at 4:26 p.m.
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PDF Problems Continue in 10.12.4, but Primarily Affect Developers

by Adam C. Engst

Numerous readers have asked me if last week’s macOS 10.12.4 update resolved more of the PDF problems we outlined in “Sierra PDF Problems Get Worse in 10.12.2 [1]” (2 January 2017). The previous 10.12.3 update addressed the most serious bug, which caused a PDF edited in Preview to lose its OCR text layer (see “Apple Releases macOS Sierra 10.12.3, iOS 10.2.1, tvOS 10.1.1, and watchOS 3.1.1 [2],” 23 January 2017).

Last week, I polled the developers who had commented on the topic for my first article. The consensus was that Apple’s rewritten-for-Sierra PDFKit framework continues to improve, while simultaneously introducing new bugs.

Christian Grunenberg of DEVONtechnologies [3] said, “Since January I have added several new workarounds and improved old workarounds. The 10.12.4 release makes only one workaround obsolete and introduces a new bug.”

He followed that up a few days later by saying, “In the last 24 hours I received various bug reports related to 10.12.4. In one case a PDF document freezes both DEVONthink and Preview; in another case pages are rendered white (in DEVONthink but also sometimes in Preview and both DEVONthink’s and Preview’s sidebar aren’t rendered at all); and in the last case PDF documents are rendered fuzzy.”

Michael Tsai of C-Command Software [4] initially outlined four bugs that Apple fixed in 10.12.4 and four that remain open, and a day later said that one of his customers had reported another crash that’s new in 10.12.4.

The story for users is somewhat better because developers are either working around the bugs they find or quietly removing functionality until PDFKit works correctly. Michael Tsai also said that there’s a middle ground of display and scrolling glitches that can’t be worked around or avoided.

Nonetheless, users continue to have problems, particularly with large or encrypted PDFs in Preview and other apps that rely on PDFKit for their PDF-related functionality. Nothing seems to be as severe as the OCR text layer deletion bug that 10.12.3 fixed, but if you experience trouble with Preview, try a different app.

For merely viewing a PDF, use the free Adobe Acrobat Reader DC [5]. If you need to manipulate a PDF, turn to Smile’s $74.95 PDFpen [6], which doesn’t use PDFKit and is thus immune from these issues. Similarly unaffected is Adobe Acrobat DC [7], which requires a subscription that costs either $24.99 per month if billed monthly or $14.99 per month billed annually (that’s $179.88 per year). Acrobat DC is also included in the full $49.99 per month Creative Cloud subscription.

To answer those who have asked if they can now upgrade to Sierra, I’d have to say that if you rely heavily on apps built on top of PDFKit for viewing and manipulating non-trivial PDFs, it’s probably worth continuing to hold off. If you mostly just read PDFs in Preview, you likely won’t hit any stumbling blocks unless you work with large or encrypted PDFs.