Hello,
If your symbology isn't coming across to ArcPad correctly (shows as # or something similar) than you're right, you're probably missing that particular font on the mobile device.
Follow these steps to identify the font and copy it to your mobile device:
1. Identify which font the symbol comes from. To do this, open the MXD which contains the symbology. In the Table of Contents, left-click on the symbol itself to open the Symbol Selector. Click on the Edit Symbol button. This will open the Symbol Property Editor which should list the font that this symbol resides in (such as esri_150.ttf).
2. Locate and copy the font. In Windows Explorer, navigate to... C:\WINDOWS\fonts. You should find the font in this location. Please note that the actual filename of the font is different than the font Name. Select the font by left-clicking it once. Copying the font must be done by going to the Edit Menu > Copy.
3. Paste the font into the font directory on the mobile device. This should be located at... \Windows\fonts.
Hope this helps.