Dan,
I have not seen any studies quantifying the DRE as a cause of elevated PSA readings. I would imaging that the short duration and slight palapation (probably similar in magnitude to a passing bowel movement) would not effect the prostate like prolonged strenuous physical activity prior to a PSA test.
I have run into ohysicians and patients who have seen false rises due to such strenuous activity prior to screening, so it is perhaps best to rest prior to your annual screening.