Thanks for your posting and using Aspose.Cells for .NET.
Please download and try the latest version:
for .NET v188.8.131.52
If the problem persists, then please provide us your source xls/xlsx file which you are converting to pdf, we will look into your issue asap.
We print as Ms-Excel print preview.
Please see the output pdf and the screenshot.
I am afraid, we do not think it is a bug. Because on the machines of other developers, Ms-Excel 2010 is showing dotted lines regardless of printer.
We render the PDF as it is shown by Ms-Excel in a Print Preview. Please check the Print Preview not the actual output.