Quality of life resources
The OSU page has several links to excellent documents that are in more of a brochure-style format. There is also a Quality of Life Scale that many people have found useful for assessing how their pet is doing.
This site has free brochures and ebooks for planning for your pet’s euthanasia, as well as resources for supporting you through the grieving process. They also run a closed FaceBook group for grieving pet families.
You will need to make an account here. It is free and gives you access to excellent video snippets on several different topics, as well as several downloadable resources for pain assessment and keeping logs. Please watch the videos that go with each download so you can see how to make the most use out of the resource.