Does solubility of acetic acid depend on the pH?
You are correct in both cases, though your reasoning isn't quite on target.  

Regardless of the pH, retinol will not be protonated or deprotonated to any significant degree (which would greatly affect it's solubility if it were). It's just a nonpolar molecule that will stay that way regardless of pH.  

Acetic acid also would not be protonated to any significant degree at low pH, but that's a mute point as it's fully miscible in water anyway.  

The one situation in which you would see deprotonation of the compound is that of acetic acid at high pH. For the most part, both acetic acid and the acetate ion produced by the basic conditions should remain highly soluble. It is possible however, that if you added enough strong base, say NaOH, to a concentrated solution of acetic acid, you could eventually precipitate sodium acetate.  

Summary, TL;DR:
You are correct that the answer to both questions is no. Acetic acid is miscible with water (so it's solubility definitely can't be increased) and it's solubility simply won't be affected by pH. If retinol could be protonated or deprotonated, that would increase it's solubility, but it can't be protonated or deprotonated to any significant degree so it is insoluble in water, regardless of pH.