I know a domain which has recently expired and is high PR, but I'm not sure if it's worth buying it. Would this be good for SEO and would the PR stay if the content is changed? Thanks for the help.
Only if you actually do something with the domain. If you leave as a parked domain, it won't do anything good for you and will slowly loose it's PR ranking
I buy them all the time for seo. Check other metrics though like PA/DA and CF/TF, number of backlinks, referring IPs, etc. Don't just rely on PR, which can easily be faked with 301's.
Also, see history of that domain. It's possible to do the mini-site with similar themes to draw people back to the site.
I use them to create my private network but I always make sure they are somewhat relevant to my niche so that it will really boost my site's backlinks.
I've heard that you can use the old articles from that exact expired domain that you plan to buy if you use the internet archive.I am not sure if it is working but it sounds great. You can use it to create a service for providing backlinks for example.
Yes it is worth buying, however as mentioned above you will need to make the necessary checks. There are pleanty of articles out there on what to look for when checking expired domains that you want to buy. -use a program like majestic to check the sites backlink profile. You will need to input the address into majestic and it will provide a number of useful metrics.
The best trick in the book is to download the original site from archive.org, so you can rebuild the pages containing the valuable links. I can help if you need assistance with that.
I think that it depends upon the actual price of the domain. I found a sweet domain with great pr ranking but it cost thousands of dollars... Only you can decide how much you can spend for the development of your website
Buying a high PR expired domain (like buying anything) is worth it only if you know what to do with it so it benefits you the most. If you don't know what to do with it, then you'd be wasting your money and time on it.
Backlinks on dropped domains may not count. Here's a quote from SEL: Full article: Do Links From Expired Domains Count With Google?