First of all, Welcome to AskUbuntu. And I suggest you to make just one question at once in order to receive the proper support, preferably in English. If you write in Spanish the answers to your question may delay until somebody translate your question.
I can partially answer your question specifically in the first point, related to your issue with the PDF Files and Chromium Browser.
Chromium Browser does not have an embedded PDF reader as Google Chrome does. That's why you won't be able to do anything in order to read your online PDF's directly on the browser and you are forced to download them insted.
You can -anyway- try to install Google Chrome, and copy the respective Google Chrome plugins to your current Chromium Browser in order to make Chromium able to open PDF's directly by following the steps provided in this previous answer by @shaneonabike, please note that in the comments @DanielHershcovich mentions that it will be better if you make a symbolic link to the plugins instead of copying, but this will be useful if you plan to keep both Google Chrome and Chromium Browser. If you plan to uninstall Google Chrome, you may wish to run the steps as mentioned by @shaneonabike, reproduced here for your convenience:
You have two solutions that I can see here (applied to Ubuntu 11.10)
[This was inspired by comments above and other sources I found]
- Install Chrome and then copy over *.so files which technically gets you around the legality issues
Here's how I did that...
- Close Chromium
- Download Chrome from Chrome distro
- Install it on your Ubuntu release
- cd /usr/lib/chromium-browser/
- sudo cp /opt/google/chrome/*.so .
- Start Chromium
Note: The new plugins never showed up in my extension listing but suddenly just started working properly. By copy all *.so you are
getting support for Flash, FFMPEG, and PDF support.
If you want to copy each individual item here is a listing of them for
you to hand pick.
- libffmpegsumo.so - ffmpeg
- libgcflashplayer.so - Flash
- libpdf.so - PDF
I must warn you that Google Chrome and its plugins are non-free software, but this workaround seems not to be harmful at all. (Tested by me).
As of your second question I can't provide you with any solution but I suggest you to open a new question about it in order to receive the proper support from other users.
Good luck!
Best Answer
To avoid this problem in future, consider installing Ubuntu with a / partition and a /home partition. Then, when you upgrade, you can either overwrite / or make a new / partition for your new Ubuntu, leaving the /home partition intact to be accessed from whichever version of Ubuntu you choose to fire up from the grub menu. I have used this strategy for all my Ubuntu installs on several machines, and it has enabled me to upgrade relatively painlessly on numerous occasions without losing personal data files.
But, I always back things up first in any case. It really is worth getting a large usb external disk to back up your /home partition or directory. You never know when your hard drive is going to go ...