I like apps that solve unique problems. You know what I'm talking about, the apps you keep on your computer and you don't use on a regular basis, but from time to time when you need them, they're awesome to have around.

jumpdf is one such application. In short, it's a free and open-source PDF viewer that has a (somewhat) unique feature - it allows you "to jump between different sections of the document frequently."

This makes it perfect for users who read a lot of PDFs and need to switch between various sections. Let's say you're reading a scientific document and you have to scroll between a section and the references section manually. Imagine scrolling over and over tens of times back and forth, quite inefficient, right?

At face value, jumpdf is kind of "meh." You don't get a fancy GUI, or menus for that matter, all you get is a main window, a PDF viewer, and that's about it.

However, there's more to jumpdf than meets the eye. While other PDF viewers offer similar features (for example marks, that allow you to record locations, and jump between them), jumpdf uses "marks" that follow the current cursor.

This makes jumping between sections similar to switching between two browser tabs. This is particularly cool because it allows you to maintain multiple views of the document (and you don't have to manually reset the marks).

As far as ease of use is concerned, there's a bit to talk about. For starters, I already mentioned that the app doesn't feature a proper GUI (at least not a classic PDF viewer GUI). Everything is controlled via keyboard.

For instance, to move up and down you can use the J and K buttons, H and L are used to move left and right, D and U to move down or up half a page, + and - to zoon and out, and so forth.

A full list of keyboard bindings, as information regarding configuration can be found on the app's GitHub repository, and I highly recommend you take a look before starting to use the app.

At the end of the day, jumpdf probably won't reach legendary status like other mega-popular PDF viewers out there. However, for those few users who are willing to try it, it will probably be perfect, especially if we're not talking about complete novices.