Google Chrome has plugin to view pdf files inside the browser.
Is there any plugin for chromium which can do this?
Do you have Google Chrome installed? If you do have it installed, you can just make a link to the libpdf.so plugin in the Chromium folder:
sudo ln -s /opt/google/chrome/libpdf.so /usr/lib/chromium-browser/
After that, enter about:plugins in Chromium, search for Chrome PDF Viewer and enable it.
If you don't have Google Chrome already installed, I suggest you to download the .deb package and extract it. Then, you must navigate to the folder data/opt/google/chrome and copy the libpdf.so to the /usr/lib/chromium-browser/. More details.