We looking for a simple, open source, web based document management system for Linux. With document management I mean the ability to store a set of files (minimally doc, xls and pdf) as a document. Associate meta data with the document like owner and version. Update and delete documents. Ability to index and search content. Authentication and the ability to authorize at least read, and possible write. If possible I would like to avoid implementations in Java or PHP, and as we use MySQL already that would work especially well for meta-data storage.

We have used Google Applications in the past but the lack of support for PDF makes it a poor fit. Other downsides include their service losing some of our spreadsheets, no concept of company owning information opposed to individual accounts, and some of our information is sensitive and we prefer keeping it in-house (passwords, contracts etc).

MediaWiki was not a good fit either as our documents is really a set opposed to be structured content (i.e. not looking for a content management system), and at least the version we had installed did not deal well with attachments.

Based on review of past questions I plan on looking into KnowledgeTree. Any other projects that we should consider?