For hosting common files it's ok. Also it is on Android too do, great to transfer files between your Windows and your phone. But if you want better security you have to subscribe a monthly offer.
Dropbox - Online Sync and File Sharing
Altarsoft PDF Reader - Altarsoft PDF Reader is a simple to use PDF files management program that allows its users to view PDF files, encrypt the files and even annotate these files as well.
Google Drive - Access and sync your files anywhere
eXPert PDF Reader - eXPert PDF Reader is a free to use PDF reader and views for the Windows operating systems.
Mega - Secure File Storage and collaboration
Cool PDF Reader - Just like its name Cool PDF Reader, this small PDF reader is a really a cool PDF reader for viewing, reading and editing PDF files for free.