Reset line weights on all objects

I've recently converted all "master" facility drawings from KeyCreator 97 to CAD2012. I want to reset all line weights. When I change the line weights on the layers in the layer properties manager, it doesn't change the line weights of the existing entities, it only sets this up for entities that will be drawn after. Is this option of resetting all line weights even feasible?

For just changing the layer lineweights to work, ALL objects will have to have a lineweight object property of "By Layer". If that is already the case, then changing the layer lineweight properties should be enough, that and a REGENALL. The only thing that really counts is how they plot. That is the final test.

Looking at the display screen in modelspace isn't going to show you much, especially if you have your lineweight display switch turned off. Even if it is on, you are only going to see a differential in lineweight and not the objects true lineweight. Paperspace is another whole matter. In paperspace the lineweights are shown in actual units, so they will look the way they actually are drawn. Of course, that is if the lines are wider than a pixel. Any lines smaller than your highest possible screen resolution will all be the same size, one pixel wide. Still, they will plot the way they are drawn.

You've provided great info, but I'm still not sure how to "reset the line weights" on all entities, which are all on different layers.

I just figured it out. I had a brain fart. I selected everything in the model space and selected the line weight desired and that basically reset the line weight for all entities.