Hi,
Unfortunately, it is hard to tell, since we can’t visit your site and test plugin work. If you don’t want to provide the link here, you can create a privite ticket on our support forum (https://support.bestwebsoft.com/). Please include a link to this post, so that we could recall the case immediately.
Also, you can try the following:
1) Try activating a standard WordPress theme for a while (Twenty Fourteen, Twenty Fifteen) and check if the problem remains.
2) Try deactivating all of your plugins except PDF & PRINT and also check if the problem is still present. If it is not, activate the plugins one-by-one, meanwhile checking, after which plugin activation the problem appears again.
3) Let us know about the results.
If the reasons are still undetected, please:
1) Provide a link to the page where the problem occurs;
2) Provide your System status. Follow the next instruction – https://docs.google.com/document/d/1Wi2X8RdRGXk9kMszQy1xItJrpN0ncXgioH935MaBKtc/edit
Sincerely,
BestWebSoft Support Team