Firstly, be prepared for a certain level of disappointment.
Video files are made up of individual frames which, when viewed consecutively, seem to give a crisp, clear picture. However (particularly when there's plenty of motion in the shot, or when the camera is panning or zooming), each individual frame may look rather 'fuzzy'. It's one of those frames which you need to capture.
You've stated that the video is 'recorded on a camera'. I'm assuming that you already know how to get the file to your Mac. Now my problem is that (apart from when studying for my journalism qualification) I've never used a Mac. Further, I don't know which operating system you're using. All I can say is that you need to:
1. transfer the video file to your Mac ;
2. play it on a suitable media player that offers a 'snapshot' facility ; and
3. (obviously?) use the 'snapshot' facility within that program.
One of my favourite media players (which is frequently recommended by other AB members, as well as BBC technology programmes) is VLC. It plays almost all video formats and offers a 'snapshot' facility. If you've got Mac OS X, you can download it here:
http://www.videolan.org/vlc/download-macosx.ht ml
Play your video file in VLC. To take a snapshot, press Command+Alt+s. (You can change that to a more convenient key combination by going to Preferences > Interface > Hotkeys settings > Advanced Options > Take video snapshot).
By default, your snapshots will be saved to the desktop. To change this, go to Preferences > Video > Video snapshot directory.
Once you've got your snapshot, you'll probably need to 'tidy things up' before you can print it.. That means using Photoshop or whatever other image manipulation program you've got.
Chris