To expand on what David Barnes provided, there can be many issues that crop when exporting marker symbols, as they are created from fonts. I've found this can be a perplexing problem to resolve, as some of the issues/complications are not well known.
1. The fonts are not on the computer that was used to create the marker symbol. Try using the original computer if possible. ArcGIS (and other programs) install their own specific fonts, so if a marker was made from them, you will need to be on that computer or font substitution will occur. That's why one can unexpectedly get "Windings" instead of the marker symbols when viewing on a different computer.
2. Embed fonts option and Convert markers to polygons are well worth exploring and can help in many situations (but see 3).
3. Not obvious - some fonts are proprietary, which means there are conditions and restrictions on using them. What this means is even if you choose the option to "Embed fonts" or to "Convert markers to polygons", the embedding/conversion will not happen if the font is proprietary - the software has been programmed not to allow it. Instead, it will default to font substitution. This was explained at an ESRI Conference Technical session (2011?). Unfortunately, there is no feedback provided to the user on exporting that font substitution was used; the export will finish out with no warning that a change was made.
4. Insidious - in some cases one can export to pdf and it will look fine on the computer it was created on. But when you send the pdf to someone else, all they see are the "Windings" For example, an interstate highway shield will become a non-sensensical winding symbol. This occurs when the recipients computer does not have the fonts that were used to make the pdf, so their computer does font substitution to allow viewing. This can be quite embarrassing for GIS folks - an awesome map is produced but the viewers are wondering why the bizarre symbology was used. And the GIS person who created the pdf has no idea it looks strange, as it looks fine on their computer. I've seen maps on many government and private web sites where this has been the case. So the moral of the story is, after exporting a figure, check it on a non-GIS computer if you plan it to be viewed by others.
Chris Donohue, GISP