Will adding .pdf attachments to transactions affect the performance of Quicken for Windows?
YEP, they're a HUGE hog on your performance due to file bloat.
Better course of action is to either manage Win folders, or get a documents manager, and use the Memo field in Q to record where you put the attachments.
I disagree with respect to performance. While a hog with respect to file size, I don’t believe program performance is unduly affected.
I agree keeping the pdf’s organized outside of Quicken is much better. Those docs inside Quicken can only be accessed through Quicken which is not a versatile document manager. Keeping them outside Quicken does keep the Quicken file and all its backups smaller ( a very good thing).