Hi you need to do the following:
Disable loopbackcheck and try again: Click Start, click Run, type
regedit, and then click OK
In Registry Editor, locate the following registry key:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa
Right-click Lsa, point to New, and then click DWORD Value. (In Win
2008, its DWORD 32bit)
Type DisableLoopbackCheck, and then press ENTER.
Right-click DisableLoopbackCheck, and then click Modify.
In the Value data box, type 1 and then click OK.
Quit Registry Editor.
You may need to restart your server.
this was taken from here:
http://social.technet.microsoft.com/Forums/bg-BG/sharepoint2010setup/thread/ee30d4e2-3509-4080-b1e1-a0f600e5cc68
EDIT
once you have done the above you need to carry on with the KB article:
http://support.microsoft.com/kb/2518465
then do the full crawl:
stsadm –o spsearch –action fullcrawlstart
To make sure its working and has crawled you need to performe a search for a pdf document. You should see any new pdf's in the search list!
Hope it helps :)