You need to have the original powerpoint to make a new pdf.
Why not enlarge the pdf displayed on the screen to 200% or so. That should make it readable.
Kees
I had class notes emailed to me that were taken from a powerpoint presentation turned PDF. Because there are so many slides per page, some are impossible to read and I want to print 4 per page as opposed to the 6 existing. Can this be changed ?

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