Oooo, you don't have very many options.
The PDF file format was originally designed to lock down everything and not allow any changes. Recent versions of Acrobat have given us some minimal editing tools for text.
But changing the text is tough even with today's tools (Acrobat 2023). Your Acrobat 9 was released in 2008, 15 years ago, and it's missing many of today's tools and utilities.
Find the Edit PDF tool panel and use it to select each block of text in the PDF, one by one. Use the edit text tool to change the font: maybe to bold (the button looks like a fat T) or to a different font on your system.
Remember, a PDF file is not a word processing file, so you can't select all the text in one selection and change it. Text is carved into individual blocks so that it can look like the original source file — and not be changed. You're kind of working against the system here.
Suggestion: before you attempt to do this, try to have the PDF's requested fonts installed on your computer. Things will go much smoother.
To see what fonts the PDF file is looking for, go to File Menu / Properties and select the Fonts tab. It will list them all. AutoCAD sometimes uses its own proprietary fonts.
Good luck with this!