Poor print quality of PDF from MacBook Pro

I have a .pdf document saved on my desktop that I can access from both my iMac and my MacBook Pro (same document, accessed through iCloud). When I print from the iMac, the print quality is great, but when I print from the MacBook Pro, the images are pixely. It is the same printer, the same WiFi network.

On the MacBook, I can see the option to change the print quality from draft to normal or best, but it does not allow me to change it (I can drag it to "best" but it immediately flips back to "normal"), and I cannot figure out which setting to change to make it possible to print in "best" quality. Please help!

All my software is up to date (including Adobe Illustrator CC), and I am running on the latest version of Mojave. My iMac is too old to run Mojave, and is running on El Capitan (but I have had this problem before updating the MacBook Pro to Mojave).