You're on a Mac, the PDF deck needs to land in Keynote, and Keynote isn't going to open a PDF as slides directly. Drag it in and you get a single image embedded in one slide — not what you wanted.
The pptx detour solves it.
Why Keynote ignores PDFs
Keynote treats PDFs as visual assets, not as slide decks. Importing a PDF gives you each page as an image you can drop onto a slide. Fine for reference, useless for editing.
To get an editable deck, you need pptx — Keynote's universally supported import format.
The two-step conversion
Run the PDF through Flint's PDF to PowerPoint, download the pptx, then double-click to open in Keynote. Keynote converts pptx to its native format on the fly.
Text boxes are editable, images are images, layout matches the original closely. Some fonts may substitute if you don't have the originals installed.
On iPad and iPhone
Same path works on iOS. Convert in Safari, save the pptx to Files, tap to open in Keynote. Works on iPad with a magic keyboard the same way as on a Mac. The conversion runs server-side so battery and storage aren't affected.
Roundtrip back to PDF
Once you've edited in Keynote, File > Export To > PDF gives you a fresh PDF. If the result needs further compression for email or sharing, compress the PDF after export. Keynote PDFs often embed full-resolution images and end up larger than they need to be.
FAQ
Will Keynote's animations work after conversion?
There are no animations to start with — PDFs are static. You can add new animations in Keynote.
What fonts will Keynote use?
Whatever you have installed. Missing fonts are substituted with Keynote's nearest match.
Can I edit on iPhone?
Yes — Keynote on iPhone opens converted pptx files. Editing on a small screen is fiddly; reserve serious revision for iPad or Mac.
What if Keynote refuses the file?
Usually a size or feature issue. Split the PDF into smaller chunks before converting.
PDF in, Keynote out. Convert your PDF to PowerPoint and open in Keynote.