Ask the sender to export the Pages file as a Word document (.docx) or PDF
Use iCloud.com and open the Pages file in the web version of Pages
Install Apple Pages on a Mac if available
Rename the file extension from .pages to .zip
Extract the .zip file to view the contents
Open the QuickLook folder to find a PDF preview if included
Use a file conversion website to convert the Pages file to DOCX or PDF
Open the converted file in Microsoft Word or another compatible app
Use LibreOffice or Google Docs after converting the file
If the file is from an older Pages version, try opening it with a newer Pages app first