my 32 bit apps like pdf reader isn't working with the updated MacOs high Sierra

Apple's Preview application is 64-bit on High Sierra and on macOS Catalina and beyond. Adobe's current Acrobat Reader DC is also 64-bit and compatible with Catalina and beyond. Your bases are covered for viewing/annotating PDFs on Catalina and beyond.

For other 32-bit applications that do not work on Catalina and beyond, see their respective vendor site for current applications that are 64-bit and stated compatible with current versions of macOS. Some vendors have chosen to not produce 64-bit applications, and others have chosen to charge for their 64-bit upgrades. This will also extend to your printer/scanner vendors as well.

32bit apps do not work for Catalina 10.15 and above. You would have to upgrade them or find a replacement.