Table borders in word looks awful in pdf

Hi, I have only one small problem. If I use some kind of dashed or dotted line or sometimes even normal thin line as a table border in my word document then the output in pdf looks grainy and awfull. The same thing happens when I am converting excel graph - the grid is damaged in pdf file. I tried to play with image compression in output settings but with no luck.

Thank you for any answer,

Tomeee23

Similar problem: I have created tables in MS Word with a double-lined border. In the pdf's the show up as single lined, but with varying thickness. It looks bad.