Files saved on CD automatically convert to Read-Only; why?

I am trying to save files to a R/W CD to be used repeatedly. I have verified
the files are not "read-only" before copying them, but they automatically
convert to "read-only" on the CD and I am unable to change them. I am also
unable to save the changed copy as a new file. I get a message that the
entire folder is "read-only." Can anyone tell me what I'm doing wrong?
Thanks.

I think all CDs are considered read-only by default.

If I'm not mistaken, it's not as simple to write a changed file to
CD-RWs as it is to a hard drive. If so, that may explain the default
read-only mode.

You can probably copy the files back to a hard drive or USB key and
then change them.