I recently was given the job to design a children's book from original illustrations drawn by the authors when they were about 10 years old. I was given a PDF of an earlier version that have been printed at a copy store and spiral bound. It had also been modified by someone else earlier with photoshop, adding some colour to the backgrounds. As it was drawn on letter sized paper and the printing of book on Amazon did not provide that format, all the illustration ad to be cleaned up and reformatted to fit a square page.
To accomplish a clean professional look, I had to separate the original illustrations from the background, paper and added photoshop elements, including the hand written text. I used quite a few techniques to do this which takes some time, but it was worth since I could then reposition all the elements to fit on the square pages. I was asked to punch up the colours as well since the copy store version had dulled the crayon colours.
Another challenge was that some of the drawings went off the edge of the page so I had to extend and add to them so they would look complete on the page.
The book can be bought on Amazon.