MediaWiki - MediaWiki is a free software wiki package written in PHP, originally for use on Wikipedia.
Google Docs - Create a new document and edit with others at the same time -- from your computer, phone or tablet. Get stuff done with or without an internet connection. Use Docs to edit Word files. Free from Google.
TiddlyWiki - a non-linear personal web notebook
Adobe Acrobat DC - Make your job easier with Adobe Acrobat DC, the trusted PDF creator. Use Acrobat to convert, edit and sign PDF files at your desk or on the go.
Confluence - Confluence is content collaboration software that changes how modern teams work
Wondershare PDFelement - All-in-one PDF editor