Mendeley allows you to share the full-text of PDFs with others by creating a private group.
Free account users are limited to creating five private groups, but can join an unlimited number of private groups. Each private group created in a free account is limited to 25 participants.
Please visit Mendeley's documentation page for more information on creating private groups
All sticky notes appear in the Annotation tab within the reference.
The Mendeley Notebook allows you to take notes and collect annotations from the PDF's you've highlighted while using Mendeley Reference Manager. You can create as many notebook pages as you want.
Please visit Mendeley's documentation page for more information on reading and annotating PDFs.