You'll need to know the fabric of your backpack.
Check these sites.
http://www.google.com/#q=pen+stains
I need help. I tried searching on google but there isn't any solutions.
How can I get rid of a bright pink pen mark on my white backpack? Also since the backpack is white, there are some dirt stains on it? What should I do?
2 answers
As for plain old dirt, there are products available at the store for upholstery and carpet spot cleaning that may help if your backpack is fabric of some sort.