how to solved Bad font object or font descriptor object in computer

That error is usually related to a damaged or invalid font object inside the PDF rather than the computer itself. If you have Acrobat Pro, try All tools > Use print production > Preflight and look for a fixup related to font problems. You can also check File > Document Properties > Fonts to see which fonts are embedded in the PDF. If the problem only happens with one PDF, also try opening a different PDF to confirm whether the issue is with that specific file.

If you are getting those errors, you have a bad PDF file, and there is nothing you can do about that. Recreate the file with a good PDF generator or complain to the original author and request a good PDF file.