This is what I have got from Foxit, they are going to fix it in next patch.
We have added command at start-up so we will not use their plug-in for now.
You can close this issue, thanks for help Saranraj!
Dear Tomislav ，
Thank you for your waiting. I just got an update from QA team and Dev team. PPDF documents will set Foxit Reader as default PDF viewer in dynamic plugins, that's why the UAC pops up. If the setting been written into registry successfully, the UAC will no pop up.
Dev team will fix in version 7.1. If everything goes well, version 7.1 will be available in January, 2015.
As a temp solution, our QA team just complied a new plugin for you, please download it from one of the following links:
For Enterprise Reader;
http://exchange.foxitsoftware.cn/plugin/EnterpriseReader/PlgDynLoader.fpi
http://exchange.foxitsoftware.cn/plugin/EnterpriseReader/PlgDynLoader_Reader.msi
The msi file can be used to destribution installation.
For Reader;
http://exchange.foxitsoftware.cn/plugin/Reader/PlgDynLoader.fpi
(Then replace the one that located in the installation directory of Foxit Reader (by default it is: "C:\Program Files\Foxit Software\Foxit Reader\plugins")
Please let us know if the replacement helps.
Thank you in advance!
Have a nice day!