Open a Pages, Numbers or Keynote File
Someone sent you a .pages and you're not on a Mac. There is usually a PDF hiding inside it — this gets it out, without uploading anything.
.pages, .numbers or .key — read in your browser, never uploaded
Read in your browser. The document never leaves your machine.
Why this works
Apple's iWork files are not really single files — they are ZIP archives with a particular internal layout. Alongside the document data, Pages, Numbers and Keynote normally save a rendered PDF preview of the whole document, so that Quick Look, Mail and Spotlight can show it without launching the app.
That preview is the entire document, fully laid out, in a format everything can read. Extracting it is instant, needs no conversion, and loses nothing visually. This page reads the archive in your browser and pulls that PDF out.
When there isn't one
Two cases. If the document was saved with "Copy audio and movies into document" turned off, or exported in certain ways, the preview may be omitted. And if the sender ticked Advanced → Save preview in document: off in Pages' preferences, there will be nothing to extract.
This page tells you plainly when the preview is absent rather than producing a broken file. If it is missing, your options are: ask the sender to export a PDF (File → Export To → PDF), open it in the free Pages on iCloud.com with any Apple ID, or use Google Docs, which will import a .pages file.
Why not just rename it to .zip
You can, and on Windows that is the manual version of this. Rename report.pages to report.zip, open it, and look for QuickLook/Preview.pdf. It works — when the file is a package rather than a flat archive, and when Windows doesn't decide the renamed file is corrupt, and when the preview is actually there. This page does the same thing, checks all three, and tells you which one failed.
What it can't do
This extracts a rendering, not the document. You get a PDF that looks exactly right and cannot be edited as a Pages document. For an editable copy you need Pages itself, iCloud, or an importer like Google Docs or LibreOffice — all of which reconstruct the layout approximately rather than exactly.