The keyboard shortcut for screenshots on Macs is:
Cursor turns into crosshairs. Drag it over an area on screen and let go. After a camera shutter sounds a PNG picture file appears on the Desktop.
This a very useful feature. Light PNG pictures can be used on web-sites and sent via email.
Screenshots of menus, windows or any particular problems you need help with are absolutely invaluable when working in a team.
Other screenshot shortcuts:
Command+Shift+3 - screenshot of the whole computer screen.
To avoid the hassle of selecting a window (any window, including an open document) or a menu when you need the picture of a particular item:
Command+Shift+4 - and hit the Space bar instead of dragging the crosshairs. The window highlights with a little camera at the top. Click on the highlighted window to get the screenshot.
Please check this previous article describing the various ways in which Pages could be shared, sent out and worked on in a team:
Sharing and teamwork in iWork/Pages