You have corrupted PDF files. They have joined Humpty Dumpty.
Obtain fresh copies. If obtained via email request that the PDFs be ZIPPED and that the ZIP file(s) be attached to email(s).
Or, have PDF provided place PDFs in a cloud file share service. Have provider email you the link(s) to the files.
Suggested services:
Free - cloud.acrobat.com (Files)
Others - Adobe Send, Creative Cloud, OneDrive, Drop Box, Google Drive, ...
Be well...