Lines in the PDF file are way too thick

When I tried to convert plots on a canvas, whether I use “save as” in the menu bar or I use “Print()” function in the script, in the converted PDF files all lines, including the plotting lines of the histograms, the axises and ticks, are so thick that they make the plots not distinguishable. Is there anyway to avoid this? Or it is just me who experience this? Thanks.


You can use:


For instance: