For files from that specific source, the password is almost always: Quick Tips for Extraction: Case Sensitivity: Make sure to type it in all lowercase.
Use a modern extraction tool like 7-Zip or WinRAR to avoid "Header Corrupt" errors.
The "paper" you are likely looking for refers to the or the RAR password required to extract the files.
Ensure you have all parts (part1, part2, etc.) in the same folder before you start the extraction of part1.