Shrink bloated PDFs
QI keep scanned copies of utility bills as PDF files. Although I haven’t changed the scanner settings since upgrading to Sierra, the scanned file sizes have shot up from around 600KB to nearly 4MB. How can I get them down to a reasonable size again?
AThis is the result of Sierra including new support for handling PDF data in its PDFKit library, which in its early releases had some serious bugs. Many of those have been fixed over successive updates, but some still remain.
Scanned PDF file size can be reduced by converting the documents, and scan settings, to greyscale or black and white, which should not affect the usefulness or legibility of most of your documents.
There are plenty of different third-party apps which can compress images in PDF files very effectively, and you should try some out to see how effective they are on your documents. Suitable products include Adobe Acrobat Pro itself, PDF Compress, and PDF Pro Compressor. Several are available through the App Store, and some offer separate free demo versions. Tweak their settings to obtain suitable file sizes without sacrificing legibility, and compress your existing scans as a batch.
Eventually, as this new version of PDFKit stabilises and it compresses embedded images properly again, its file sizes should reduce to those achieved in El Capitan. However, custom compression should bring you some benefits even then, and may be worth using on your old files created in El Capitan too. If you’re going to keep PDF records, it’s worth taking the trouble to optimise their storage.