Hope you are doing well and sorry for the trouble. As described you are unable to open the PDF and getting the unexpected error.
I have tried to reproduce the issue on my end with Win 10 and Adobe Acrobat Reader DC version 21.01.20145 and the PDFs are opening fine.
What is the version of Acrobat Reader 2017 you are using? To check the version go to Help > About Acrobat and make sure you have the latest version installed. You may also download the patch manually from the link: https://www.adobe.com/devnet-docs/acrobatetk/tools/ReleaseNotesDC/index.html and see if that helps.
Also, you may try using the Acrobat Reader DC (freeware application) https://get.adobe.com/reader/ and see if that helps.