This tutorial was excellent, however I wanted to note something for future readers/watchers. I am using this on some PDFs of architectural plans. They are relatively large with very detailed text. I initially followed this video exactly, including using ImageMagick. The time to convert and process PDFs was okay locally but VERY slow in production. I'm using a cheap option on Render and don't want to pay for more while I get a product started. I was also already using Vips elsewhere in my app. On a whim, I decided to remove MiniMagick and use Vips (using ImageProcessing::Vips doesn't have a way to convert PDFs to image in a way I could get to work) to fix a slightly different problem. This cut my processing time down by a HUGE amount.

TL;DR: Use Vips instead of MiniMagick if you're finding that converting images are slow or the image quality is insufficient for your purposes.