I ask NOT about court opinions. Downloading or online reading is more convenient and favoured than physical copies.
Where can I read submissions to the court for both sides of a case, written by litigators?
The answer by user3344003 is accurate.
But, in state and local courts usually only lawyers have access to the online filing system where briefs and other pleadings are filed by lawyers. Access to those documents by non-lawyers to those materials is quite cumbersome in most states.
Also, some cases have access limited to lawyers and parties for confidentiality purposes. Even in cases whose pleadings are open to the public for lawyers, there is usually a small fee for accessing court documents in a case. In Colorado, it costs $10 to get two weeks of access to files in a case where you are not a party or a lawyer.
If you are interested in Michigan state court, the records of some of my cases are available here (defamation) and here (personal protection order). These include hearing transcripts as well as filings from both parties in trial, appellate, and supreme court.
I am a pro se litigant, and I am sure you will notice my progress from the complaint all the way up to my briefs in the supreme courts.
There are two other cases I will upload, but first I need to redact a bunch of calumnies the defendant wrote about me (and which prompted me to file suit). I just haven't had the time to perform the redaction.