What is forward pressure and how to adjust din?

You can adjust them yourself. HOWEVER, only if you are confident in what you are doing and know exactly what to look for when setting forward pressure.

Moving your din up and down with a screwdriver is easy and as long as you go slowly and make sure to make them all the same you won't have problems.

With forward pressure it varies binding to binding but it usually has to do with adjusting your heel piece back and forth. There is also almost always some sort of indicator on the heel piece that lets you know if it's set right or not.

What kind of bindings do you have?
If they were mounted and set at a shop then forward pressure should be good regardless of what you change your DIN too. But some bindings can be weird and if you don't set it properly you risk a lot of serious injuries especially with your knee's.

I have Tyrolia Peak 11 bindings. I originally had my din set at 6, and I skied on them for a while with no problems, but after access to a scale I guess I overestimated my weight. So I took a screwdriver and set both the toe and heel pieces to 1 din lower.

Forward pressure is exactly like it sounds: the forward pressure exerted from your heelpiece on your boot which is dictated by the micro bsl adjustment area where you have your heel set. If forward pressure is too low, you'll prerelease because your boot is too loose in the binding. If it's too high, you'll prerelease because as soon as your boot is knocked off center in the binding, your toe piece will be unable to recenter it under the extra pressure from your heelpiece, causing your toe to slip out the side.

So if I had them professionally mounted then I should be fine taking a screwdriver and adjusting the DINs? If so, that's good news.

Most likely, as long ad you haven't already fucked with the heel track/bsl adjustment.

If all you have done is turn the DINs down to 5 then your golden man, Go shred!