I have found the following issue with some of my test Visio files when converting to PDF.
In BldgPlan.vsd from ShapesDrawnIncorrectColor.zip (990.2 KB), some of the shapes come through with either light grey lines or are drawn with a ligher line weight, they appear grey when they should be black like others on the page.
In CrimeScene.vsd from ShapesDrawnIncorrectColor.zip (990.2 KB), some of the evidence shapes are drawn incorrectly, and others with the light grey outline when they should be black. Also, the dotted lines spacing in the PDF is narrower than the VSD file, making the lines look almost solid when the PDF is opened. Only by zooming in was I able to determine that they were dotted.