You can, just keep in mind that a UDT added to any module besides Library Master (SYS) will be have data stored on a per company basis, just like the regular modules. So in other words, adding the UDT to Library Master will cause its data to be shared across all companies in the installation.

You may want to either have the UDT created in SYS with a column to indicate the company or you can create the UDT under a specific module, such as GL, so the data is maintained separately. If you use the latter, than the report should automatically point to the current company's UDT when ran from the sage 100 menu. If you use the former, you will need to devise a way to select just the current company's records. If the report is added to the menu, then you should be able to create a special formula called CompanyCode with a default value equal to a blank string ("") that sage 100 will populate when processed and you can use the formula in the report's record selection criteria.

I appreciate you responding! Admittedly, your notes went right over my head. The UDT was setup long ago by someone else, and I believe they were set up at the system level, because I can see other, irrelevant location codes in this specific company that belong to another company. 
I guess what I don't understand is how to even add the option to choose the user-defined location code when setting up my custom financial report. I would think I'd be able to add a line in the "Account Ranges" screen like you can for other reports like GL Detail Report, etc. I would like to see the UDF here, so I can tell the financial report to only pull the company transactions specified. 

You're not going to get the UDT's values into that selection grid unless they exist as a value in a UDF or standard field in the primary data table for the report.

What you can do though is if the UDT has been added to the Crystal Report, you can modify the Crystal Report to include a runtime parameter that would allow the user to choose a value. This parameter prompt would appear after you click Print/Preview.