Here is the reality check. Merriam-Webster does not sell an official PDF of the Collegiate Dictionary, 12th Edition.
Merriam-Webster’s business model relies on three pillars:
Selling a DRM-free (or even DRM-locked) PDF would cannibalize their print and subscription sales. If you go to Merriam-Webster's official store, you will find the Hardcover 12th Edition for roughly $26–$30. You will not find a PDF. Merriam Webster Collegiate Dictionary 12th Edition Pdf
Before you spend hours hunting for a PDF, consider this: A dictionary is not a novel. The way you use a dictionary differs from a linear text.
For serious writers, students, and logophiles, a static PDF of a dictionary is a last resort, not a first choice. Here is the reality check
A common point of confusion for many seekers of this reference is the edition number.
Therefore, if you are looking for the most recent version of the Collegiate series, the 11th Edition is the text you require. Selling a DRM-free (or even DRM-locked) PDF would
If you own a Kindle, buy the Kindle edition of the 12th edition (available on Amazon). This functions similarly to a PDF (paginated, searchable) but is legally licensed and syncs across devices.