I would like to cancel my purchase

Hi,

Which product are you referring to? If Creative Cloud or Acrobat DC, then you can cancel your subscription by following the instructions given on this Adobe help page:

https://helpx.adobe.com/manage-account/using/cancel-subscription.html

When scrolling down that page, you'll see a section entitled "Am I eligible for a refund?," which should answer that as well.

If it's a non-subscription product you mean, then refer to this page instead:

https://helpx.adobe.com/x-productkb/policy-pricing/return-cancel-or-change-order.html

Hope that helps.