Hi Lisa, great to hear you've sorted the printing

To put lines around my pics I use the stroke command. Edit/Stroke (I think its in the edit menu - I'm on the laptop and can't check at the moment)

You need to select the whole image first, Select/All, then go to Edit/Stroke. In the dialogue box you can set the thickness of the line in pixels and where it is placed ie. inside the selection (overrighting the edge of the image) or outside the selection (making the image a few pixels bigger. You can also choose the colour of the lines.

To make two (or more) lines of different colours just keep repeating the above actions so to place a thin white line around the image with a wide black border outside that - select the image, go to edit/stroke choose white as the colour, pixel width to 2 and inside as the position and click OK. A 2 pixel line apears around the image. Now repeat the steps but this time choose black, 6 pixels and outside and a 6 pixel black border is placed outside the first white line.

Hope this answers your question

Edit: GDN's way works in a similar fasion to mine but he types quicker than me!