Welcome to our forums and thanks for the enquiry.
Text inside PDF file is quite a complex structure, and there are components that guarantee that the text will be displayed well, but there is a separate portion that allows text to be extracted correctly. That last bit of info can be skipped if a minimal file size is required, or if text extraction is to be prevented. Unfortunately there is little we can do - as the problem is with the file and not at our end. Adobe as well is unable to copy text from this file correctly:
You can e.g. try to OCR those pages - and see if you can select text after this, or you can contact the document producer and tell them of the troubles you are experiencing and they might be able to provide another version with all text information included.