The gap before H1B with CPT

I'm internship in a company with CPT and get H1-B with lucky. However my CPT will end one month before October 1st. I have no OPT becasue I applied it several years before with my careless , although I never use it. For this one month gap, I want to use my PTO to fill in it. I want to make sure it is legal for me to get PTO salary and still keep my right status(F-1) in the United States until octobor 1st.