In most charts there is the letter D next to the VOR freq. What does this mean? I assume the H and L in brackets in other charts mean high and low VORs (correct me if im wrong). But what does the D itself stand for?
Since you're specifically referencing a Jeppesen chart, we'll go right to the source.
Jeppesen's "Introduction to Jeppesen Navigation Charts" has a glossary and explanation of all terms and symbols.
The answer to your question reads as follows:
1 — VORDME. Low and High/Low charts include a Compass Rose with VHF Navaids. Shadow box indicates navaid is airway component, with frequency, identifier, Morse code and INS coordinates. Small "D" indicates DME/TACAN. Class indicated by: (T) Terminal, (L) Low, (H) High.
So, the D indicates that the VOR has a co-located DME radio.
(and, no need for correction to your assumption: the H and L in brackets do, indeed, refer to a High or Low class of VFR)