On The Level: Creating extra attic space can work if done correctly

We have just combined two households and we are buried in things we don't want to throw away but want to store. I was wondering if it is possible to install plywood up in my attic space to use it for storage. I currently have a hatch that I have to remove and bring a ladder to get up there. I'm thinking about installing a pull down stairway and putting plywood on the floor to store things. Is this feasible? I've heard that the type of roof support system that I have is not designed to have plywood attached to the floor. Can I?

I know it's hard to look at that access panel in the ceiling of your upstairs hall or...