I made my first PA-31 checklist from the Piper POH, can't go wrong using what they advise, add whatever you want extra you think is good. The only PDF checklists I have are propriety property to certain companies and fit in with their operational philosophy, ie some things were done differently because we did maintenance differently, two crew operations, so on. Things like leaning procedure, cool down procedure, power settings for climb, cruise descent all might be linked to certain monitoring we had so not a good idea to transpose to your own flying without the big picture. The POH is designed for the basic airplane operated by the simple user.