99% of my work is for online use.

I have one client that want an ad printed in amagazine.
It's a small ad, 2.25 x 8.5 in. and contains to small images. They need this work as a pdf 300 dpi or better and CMYK colors.


Everything is fine except for the images. After I reduce them they are low res images. They are originally 2560 x 1920.
What is the correct way to reduce these and still keep the high resolution suitable for printing?
I did this:
I make a bitmap copy of my native image and sizeed it to 2.25 inces wide (it's a portion of the original pic) in the bitmap resolution box. I noticed the resolution default to 96 dpi. I don't know much about printing...is this correct?. Well…it can’t be since I no longer have a high re spic.

I export the ad as a pdf at 300 dpi.

Thanks in advance for any help.

Tom