I would suggest a tool called RecentX which is a file launcher that also keeps record of recently opened documents not just pdf) so that you can quickly re-open them - http://www.conceptworld.com/RecentX
RecentX supports tagging of clipboard items. Although it has single clipboard history, you can tag your items so that with 2 clicks you can get any set of items - http://www.conceptworld.com/RecentX
Don't know if this work for you. RecentX has clipboard history manager that allows tagging. So you can copy different text and tag them and do your analytics part very easily. RecentX is here: http://www.conceptworld.com/RecentX
RecentX can do this. It has a clipboard manager. You can configure it to not remember the clipboard items when certain apps are active. Like Keepass etc - http://www.conceptworld.com/RecentX
If you want to quickly search and launch any file or folder you can use RecentX. You can also tag files and folders to group and organize them. You can open with any external app by using the "Open With" feature - http://www.conceptworld.com/RecentX
Like @OgdruJahad suggested, you can use tagging. But Windows tagging doesn't support all files.
RecentX does support tagging on files and folders. You can try that: http://www.conceptworld.com/RecentX