Hi Adminer,
I have setup a small test page with a PDF file obfuscated in different ways (extension, MIME type...).
http://vaemendis.net/ubooquity/misc/kindletest/
Try it with your Kindle browser and let me know if one of these tricks works. (I don't own a Kindle myself)
About the broken link: thanks, I fixed it.
About a Polish translation: I appreciate the offer but I don't think Ubooquity is complex enough to require a translation. There is not much text, and any person capable of installing a server probably reads english anyway.
About file upload: the principle of Ubooquity is to be a content server that makes files available on the network, but that never modifies these files. That's a principle I want to uphold in order to keep Ubooquity simple and easy to use.
Allowing file upload and more generally file management is a much bigger task than what I want to and can do.
So to import your files, the easiest and fastest way is probably to install a
web file manager (or use a FTP client).
By the way, the name displayed by Ubooquity are the ones found in the metadata of the book. The file name is used only if no metadata has been found.