Ummm.... explain to the designer that the file size needs to come in at 50k or LESS. 2-3 fonts maximum, and use COMMON fonts like Arial, Times, etc. as suggested above. Images not over 144dpi resolution (72dpi is better).
That should shrink the file size considerably. If the designer can't do that, find a new designer.
Your main problem is that your newsletter is created by a "designer".
Nonsense. ;) I'm a designer. I can create a small, nice looking PDF when necessary. The main problem is that the designer doesn't seem to know the web from a hole in the ground.