Lightroom: Quality of Slideshow images

So I have these RAW+Lightroom adjusted images in a collection. I go to the slideshow module and prepare the presentation as I would like it, or as appropriate. I choose "export" and I choose "screen" for size, or whatever size I would like. After the export and launching the pdf, the pics just do not look the same as they did on my screen in lightroom for a 1:1 preview where all adjustments are visible. I already understand that the slideshow exports jpegs in sRGB. Color is not a problem.

I am concerned about this because if I send to a client a slideshow that doesn't look sharp on their screen, there will be problems.

Please keep in mind, I have an iMac and in all other programs, the images look fine (even with the iMac preview program). The quality I am having a problem with is consistent from computer to computer (i.e. Mac and PC).

Thanks for any input.

Sounds like Adobe's Acrobat Reader is resizing the pics because you chose "screen" as your output size. Pic a size like 800x600 and see if it gets better. Make sure your Acrobat reader is displaying the image at 100% too.