In which file can I find and edit CiviPledge CSS styling to make the form look more in line with the rest of my site? Thanks!
It's best to not edit the files directly, but to create your own file. Otherwise it will get overwritten with each upgrade you do. In the version I'm using, I can set the custom CSS file here:
I use the "inspect" option in Chrome to see what CSS is being applied, then I copy it into my custom css file, and edit it.
In addition to Jenni Simonis's answer about creating a global custom civicrm CSS file, I restyled our contribution pages and explained the process in this answer. I'm sure something similar could apply to pledges with your own styles. My purpose for using a separate CSS file (rather than my global custom civi css) for contributions was to have more control over which price sets it applied to.