The particular problem is not certain from your description, but here's what happens with PTC output.
PDF has the ability to set the scale of the output, but PTC choses not to use it**. Instead PTC pre-scales the coordinates of the output, but they do not scale the widths of the curves. This means that large areas plotted to small pages directly from ProE will have lines that are that are not proportional. The cure is to always plot to the full scale output and use a PDF viewer to perform the scaling.
In addition, it is the norm that if a pentable is invoked, any directly applied line widths will be ignored.
On the Adobe end of things, there are two modes. In one, Acrobat or Reader will ignore assigned thicknesses, which compensates for this defect in PTC's output. In the other, the thicknesses are shown as the document has them.Various versions of Reader and Acrobat have had various names for this mode.
If sent to Postscript interpreters, Adobe software defaults to plotting at least a minimum thickness. If you ask for a line that is 1/1000 inch wide it will be 1/300 inch on a 300dpi printer and 1/600 inch on a 600dpi printer. On screen it will either be anti-aliased (because most screens have been much lower dpi) or set to 1 pixel, depending on the mode.
PTC also defaults to flintstone style stroke terminators - to make smooth letters, the setlinecap and setlinejoin should both be 1. As can be seen in Postscript output they choose the least attractive combination: stumped caps and beveled joins. They chose to not fix the Postscript output up to WF5, but did include settings for PDF output.
I recommend reading Adobe's The PostScript Language Tutorial and Cookbook (aka Blue Book), available at no cost at the Adobe PostScript SDK Archive. I also saw a government site that may have a download in a Google search for "Adobe Blue Book"
**The default unit in Postscript and PDF is 1/72 inch. In the Postscript header PTC uses "72 72 scale" to move it from 1/72 inch units to inch units. It would be trivial to also include a scale modifier for scaling the contents of the page, but PTC choses not to. I can think of no reason for wanting to force the width of lines to remain constant regardless of the scale of the image. Perhaps there is one, but most people think it just makes the drawing look screwed up.PTC compiles the Postscript header and footer into their software, limiting the ability to fix the setlinejoin and setlinecap.
This scaling defect led me to create thin_pen settings so that D-Size drawings could be directly printed to the A-sized DEC LN03 Postscript printer in a minute or so rather than wait 20 minutes for the Draftmaster to drag a pen around the paper. This was before Acrobat was available. As too often happens, a tool developed to compensate for a defect ends up being used to create defective products after the circumstances change - in this case drawings that are unreadable unless the 'ignore line thickness' mode of Acrobat or Reader is turned on, because the line width is too small. It's a good thing Adobe is there to cover for bad use of a good tool.
