Once you have cleaned your site and it is up and running again you need to harden up your WordPress installation or this one is just going to come back. Vistor Tracker injection is a very recent malware campaign and has gained momentum over the last few days – This was a warning we published this morning – Visitor Tracker Malware Warning
Alternatively you could remove the URL of the PDF’s you want removed from Googles index by going to Google Webmaster Tools>Google Index>Remove URL’s
This takes a few hours and it will dissapear from the the search results
Can you provide your website url
You might like to see Pootle Press CSS hacks and keep for future use – It is aimed at the Woothemes canvas theme but many of the tips work on most WP themes. 65 Tips Tricks & CSS Tweaks