In v 8.5.xxxx this can be accomplished by making some additions to the C:\Documents and Settings\All Users\Application Data\QlikTech\Publisher\AccesspointService\Settings.xml
<Allow Extension=".pdf" />
Also if file resides somewhere other than the AccessPoint documents folder you can add that directory inside section:
<AddDirectory Path="YourDirectoryPath" />
Then restart the AccessPoint Service under run >services.msc for settings to take place.