Marilyn:
I would photograph the picture >from above with the
picture flat on the ground- no flash. Do this outside
in the mid morning or later in the afternoon, on the
north side of the house so that there is no direct
light on the subject. I have had good luck with this
technique. (I have had an acceptable photograph of my
great grandparents, taken this way, for decades. (I
also have the originals now as my aunt left them to me
when she passed away.)
Another technique to use if you have a camera that
accepts filters, is to use a polarizing filter. They
are inexpensive, allow you to photograph through glass
without glare (not only framed photographs, but
display cases or shop windows). In fact, many serious
photographers will leave their polorizing lens on
their camera all the time, to cut glare and to protect
the surface of their more expensive lenses.
Mark Shofron
Mesa Arizona