Kevin is right....you will drive yourself "mad".
Pro creates dimensions on everything as soon as geometry is placed. As Mark stated, all geometries are dimensioned with "weak" dimensions that are light grey. You can long right click on them and make them "strong" dimensions which will define and constrain your design intent,
But even if dimensions are "strong", they does NOT mean that you cannot drag the geometry and change the dimensions. In order for the geometry not to change, you have to "lock" the dimensions. While in a sketch, you can go to "Sketch"->"Options" and checkmark for all user-defined dimensions to be locked. That way, they will not be able to be moved.
Pro is different from anything else out there....it takes getting accustomed to, and even then, you will miss features from other 3D programs you have used.
Pro/E (Creo) can be setup so that modified dimensions automatically become locked. Our commercial customers typically set this option to YES, however, based on input from our academic university customers we have have left the option at the default NO setting.
If you would like to turn on this behavior, use the following config.pro option:
I hope this helps. Personally, I sometimes like this set to YES and other times I like it set to NO, it all depends on what I am doing and the type of features I am working with.