There have already been many questions about this in the past, here for example. But I feel like many of them are probably somewhat outdated, after all, 2018 is getting closer rapidly.
I'm only in third semester, but I already remark, that I'm about to gather tons of pdf's, a good amount of them such, that I'd like to keep for later reading. I'm looking for a PDF tool that gives me the following features:
Fluent organizing of documents. I want to have folders/subfolders. If I want to move documents from one to another folder this must go very quickly without too much hacking. The structure should be independent of the actual file structure on my hard drive.
A stable in-program PDF viewer, or the possibility to set a default one that opens Documents. Highlighting. I like highlighting, in different colors, and I want to select the color without having to go through a bunch of select options to switch the highlight color. For me different colors have different meaning, so this must go quickly too. The same with notes. The option to add text box with a shortcut would be highly appreciated.
Speed. I downloaded Mendeley. If Skim is able to fluently display a PDF I explect the same for a PDF organizing tool. I don't want to wait 0.8s for a page to load if I'm rapidly scrolling through a document. The same with zooming. I want to use my trackpad to zoom, or to press ctrl while using the mouse is fine too. But having to click on +/- zoom option is certainly not an option.
Search options. On first look, I very much liked how Mendeley displays so many informations about the PDF's and I can only imagine how desirable it becomes to search documents for exmaple based on authors.
The ability to form groups/folders, that I can share with others.
Must be available on macOS, support for Ubuntu would be a plus.
I remarked, that many questions were about Bibtex stuff too. I have very few experience with references using Latex, but I guess sooner or later I'll reach the point where I need those things.