How can we encrypt a file to be just readable (and not writable) after decryption? Is it possible to encrypt a file (e.g., a text document) such that when a user decrypts it, he/she be able to just read the file and not be able to change the content of the file?

I mean, the result of decryption be a read-only file. I think any modification can be detected using message authentication code. I am looking for a method to prevent the user from modifying the decrypted file.
A "file" is a convenient metaphor for a sequence of bits on a specific file system. Your copy of foo.bar is not the same as my copy of foo.bar, even if they contain the same data. And short of exploiting a bug in my system (illegal in many jurisdictions) there is no way for anyone else to dictate what I do with my copy of files. So in general, no, this is not possible if I have control over the system the file is on. Conversely, if you control the hardware, software and I/O devices of a system you can give me access to look at the contents of the file but not change it in any way.

However, if the goal is to preserve authenticity the solution is readily available: Use a hash-based cryptographic signature and ensure that anyone or anything that reads the resulting file verifies that the signature belongs to the right person.