Question: I have a huge collection of PDF. Mostly it consists of research papers, of self-created documents but also of scanned documents.

Right now I drop them all in one folder and give them precise names with tags in the filename.

But even that gets impractical, so **I am looking for a PDF library management application**. I am thinking of something like [Yep](http://www.ironicsoftware.com/yep/) for Mac, with the following features:

* PDF cover browsing (with large preview, larger than Nautilus allows)
* tagging of PDF (data should be readable cross-platform)
* possibility to share across network (thus rather flat files than database)
* if possible: cross-platform

Mendeley seemed to be a good choice, but I am not only having academic papers and don't want to fill it all metadata that is required there.

The only alternative I could find thus far is [Shoka](http://www.mauropiccini.it/shoka/), but the features are limited and developments seems to have stopped already.

Answer: 
One possibility is [Calibre](http://calibre-ebook.com).

It is an ebook management program which permits conversion to various ebook formats but is cross-platform and can manage databases of pdf files (and not only).

If you decide to install I suggest you do so manually as the version in the repos is not very up to date. Follow the instructions on the site.

A screenshot:
![enter image description here](https://i.stack.imgur.com/2Bqfg.png)

Another possibility is [Zotero](http://www.zotero.org/)

It is is bibliography manager but permits adding book details directly through a browser Amazon.com and other sites, pdf attachments and more.

![Zotero Chrome extension](https://i.stack.imgur.com/xkCOx.png)

To import the pdf's into Zotero you can [see this page](http://libguides.northwestern.edu/content.php?pid=68444&sid=1179558).
**[Referencer](http://packages.ubuntu.com/de/lucid/referencer)** (GNOME) is a simple tool for managing document collections. 

Tagging is possible.

It tries to find metadata on arXiv or via DOI, but you can add metadata manually too, of course.

But I guess development stopped.