opening a compressed .pdf

@Hawki67 

• "Compress" can mean two things: 
  It's a zipped file and needs to be unzipped first.
  https://support.microsoft.com/en-us/windows/zip-and-unzip-files-8d28fa72-f2f9-712f-67df-f80cf89fd4e5
• The size was reduced to make it smaller.
  https://acrobat.adobe.com/link/acrobat/compress-pdf

How was it compressed and who compressed it? Please show a screenshot of the error message you get when you try to open it.

Jane