[Donna from Florida]

I also had a table that had disappearing lines when I made a PDF from an MS Word 2007 document. The lines would appear or disappear depending on the zoom level using for viewing the PDF.

I was able to resolve this problem by creating a new table using Table - Insert Table and dragging to select the number of rows and columns that were used in the original table. I then copied the text from the original table and deleted the original table. The fresh table shows up properly in the PDF at various zoom levels.