problems with uploading the pdf with the plugin

Hi! I have bought the plugin to visualize flipbook on my WordPress. Once installed (including entering the key), the plugin doesn’t upload my pdf file – and it isn’t about the size! The message it displays is: “An error occurred in the upload. Please try again later.”

I am really in trouble!! Does anybody knows how to solve this?

You should try to contact the author who may be able to help you with this.

Hope you can get it resolved.