The lack of navigation features in the PDF reader becomes a problem when navigating among more than a few papers, as it is common to do when deep-diving on a topic.
Bookmarks are very helpful to quickly go to a particular definition or section in a paper; they would help with reviewing literature on a topic and building up a list of touchstones as a reference.
Snapshots (similar to Skim) would allow me to keep a particular part of a paper open in a separate window for continuous reference; I find myself having to scroll quite a bit when following informal explanations that relate to formal definitions given later or earlier in a paper.
Back/forward navigation within a PDF would make it much simpler to go back to where you were when following up on a clickable reference or back to what you've been reading before going to a bookmark.
Dear Dr. Kavukçuoğlu,
Please could you tell me if you're using the iOS and/or Mac PaperShip app?
As you mentionned Skim, I think it's the mac app but I'm not sure.
Bookmarks are not easy to manage nor to sync between devices. So I don't think we have resources to do so right now.
Regarding the back button, it's more related to find a place where add this buttons into the interface ;)
Already too much features...
Julien Therier, Ph.D.
My comments were about the Mac version; I use both Mac and iPad versions.
If I had to assign a priority to the individual navigation features, I would say synced bookmarks is first, back/forward navigation within PDF is second and snapshots are third.
I'm pleasantly surprised that you are already thinking about UI clutter. However, the reader toolbar has a spare five buttons, leaving quite a bit of space for navigation features, I think. At the minimum, you could consider adding the standard back/forward navigation keyboard shortcuts ( ⌘+[ and ⌘-] ) to the Mac version.