We are a production company who have someone design a flyer for us but then we may want to resize the flyer, remove some elements etc etc etc we would like to do this ourselves but don't know which software to go for??? can you help??
That depends on how the files were created -- if they're vector files, you probably need Illustrator. If they are page layout files, you probably need InDesign. If they're photographs, or were created in Photoshop, then you need Photoshop.