I received some translated pdfs from Taiwan just now. They opened up ok in Adobe Acrobat & Adobe Reader but they failed to open (or failed to display the Chinese text) in other programs. I find the best way to ‘clean’ the PDFs is to print to Adobe PDF printer from Reader/Acrobat. It recreates the file but only with the content that was sent to the printer. The result still recognises text and images but as the new file has been created from scratch it can be opened in other programs.
To bulk do this:
- Make sure you set Adobe PDF driver Printing Preferences to what you want (including setting a destination folder)
- In Acrobat, in Advanced Menu > Document processing > Batch processing you can run a batch sequence that will print all the files in a specified folder.