The more I think about your issue (and I've thought about it a lot), the more of a fool's errand it appears to be.
Here's why: If you do not have a full and complete browsing history to refer to, there is no way to compare pages you've visited to documents you've saved and/or printed from those pages.
Since version 4, Firefox will only retain browsing history until Firefox decides that the compiled history effects its performance. (This has come up innumerable times in the Mozilla forums.) I never delete my browsing history, have been using FF as my default browser since v2 in 2006, and still only have history from early January, 2011. I have no idea how Safari treats history.
The only thing I can think of is that you copy your entire browsing history, such as it is, from Firefox > Show All History, manually enter all of the URLs into a spreadsheet, then compile all of the URLs from your printed and saved PDF documents and manually enter them into a spreadsheet, and somehow, try to determine what duplicates exist. The list will absolutely be incomplete, but if you are on a mission to find a mythical needle in a mythical haystack, I admire that, and all I can do is wish you the very best of luck.
And I do.