Do people just generally get 5 extra pics when they get their other PR pictures taken (for a total of 9) or can you use something else (e.g., take a pic with a camera and get 5 4x6 prints made?
You CANNOT use 4 x 6 prints for PR applications! Give them what they ask for in the size they tell you. The information will be in your Region Specific form.
I know that the 4 prints for the PR application have to be the specified size - I wanted to know if the 5 pics I have to give to the doctor need to be any particular size.
Yes, they need to follow the same specifications as the PR pictures. I don't know your region but this was included in the instructions for mine. Hope that helps.
Once you get the medical request the original form is attached with your photo with a seal of the Visa office. You can submit the same size photo. You don't have to change the size of the photo every time.