Avoid Using macOS 10.12.2’s Preview App For Editing PDFs – Here’s Why
If you regularly make use of the Preview app in macOS 10.12.2 Sierra, then you might want to reconsider things.
Preview App in macOS 10.12.2 Can Cause Corruption Issues, Avoid Using it Until Things Are Fixed
Preview is a powerful app in macOS that gets a lot of things done in a snap. From making quick edits to a photo or editing a PDF, you can achieve your goals swiftly using the Preview app. However, it seems as though the app is not so great when it comes to editing PDFs if you happen to be using macOS Sierra 10.12.2. The reason for that is simple: Apple has reworked the PDFKit framework which many developers rely on, breaking functionality in a lot of cases. Basically, if you rely on editing PDFs using Preview, then it is highly recommended to take a backup of the file first then make edits on a newer file so that nothing gets lost or corrupted during the editing process.
Here's what Adam Engst from TidBITS had to say on the matter:
It pains me to say this, speaking as the co-author of "Take Control of Preview," but I have to recommend that Sierra users avoid using Preview to edit PDF documents until Apple fixes these bugs. If editing a PDF in Preview in unavoidable, be sure to work only on a copy of the file and retain the original in case editing introduces corruption of any sort.
The Preview app in macOS 10.12.2 Sierra has been dubbed as a 'work in progress':
Apple wants to use a common foundation for both iOS and macOS. However, it was released way too early, and for the first time (at least in my experience) Apple deprecated several features without caring about compatibility. And to make things worse, lots of former features are now broken or not implemented at all, meaning that we had to add lots of workarounds or implement stuff on our own. And there’s still work left to be done.
10.12.2 introduces new issues (it seems that Apple wants to fix at least the broken compatibility now) and of course fixed almost none of the other issues. It’s not only DEVONthink — a lot of other applications (such as EndNote, Skim, Bookends, and EagleFiler) are also affected.
So, until Apple fixes things in a later macOS Sierra update, it's recommended to take a backup of everything before making edits in a PDF document. Till then, keep your documents safe.