Lines in vector file (.WMF) thicken greatly when exporting to .pdf via Acrobat

Hi,

I translate .dwg files, convert sections of them to .wmf files and paste them into Word documents. Then, I export the Word document to .pdf via Acrobat. However, the lines in the vector file thicken greatly, such that it is nearly impossible to read the .pdf. How would I fix this? Top is .Word, bottom is .pdf.

Thanks in advance!