ShipStation's packing slip editor recognizes a few standard fonts, so it's easy to change the font type for your packing slip. Arial is the default, but you can use other websafe fonts like Verdana, Georgia, Palatino, etc. Here's a handy external link to some websafe fonts to help you decide!
*Please note that you need to be on a Silver or higher plan to customize your packing slips.
Once you've settled on a font or font family, you'll only need to copy and paste a few lines of code into your 8.5" x 11" packing slip template(s).
Head to your Account Settings (the wrench icon in the upper right).
Next, select Templates and then Packing Slips from the sidebar on the left.
Either copy or edit an existing template, and the Order Header section should open by default.
At the very top of this section, you will need to insert the code below (modified for your font-family of choice):
font-family: Georgia, serif;
After you do that, the section should look like this:
Click Save, and your customized packing slip will be available to use!