Bottom of pants leg leaves marks in skin and they aren't even tight like socks. is this a potential sign of edema from heart failure or kidney failure?

It is a sign of possible edema which may be from venous insufficiency, heart,kidney or liver problems. If you observe that apparent leg or ankle swelling goes away overnight, edema seems likely and warrants an evaluation by your physician or a specialist in internal medicine. Appropriate testing will be done including blood tests, urinalysis and leg ultrasound depending upon the assessment.

No. enough pressure on skin will leave marks on normal skin too.