I understand this is a bit of a silly question, but I have some pdf portfolios I sent to graduate schools for applications, and I want to make absolutely sure that unsubscribing from InDesign and deleting it won't affect the grad school's ability to view the pdfs I sent them. The pdfs were exported from InDesign.
Yes. You can remove InDesign but you (and the schools) will need to have a copy of (free) Adobe Reader installed to see the PDFs.
The nice thing about the subscription model is that you can always reactivate for a month if you realize your documents need a major overhaul in InDesign. Then you can deactivate after creating new PDFs.