Is a PDF ever the right choice for an invitation?
When you want something rich and printable, or for a webinar where the registration behind the invitation is a real form that captures names and emails, a PDF has its place. For an ordinary party though, it stays a static document: it will not collect replies against your guest list or refresh a changed detail, so a link page serves better.
How does QR check-in work without a special machine?
Each guest receives a personal QR with their invitation. At the door you open the live list and scan the code they present, which marks that name as arrived. There is nothing extra for the guest to do or install; the QR simply came alongside the invite.
Can I still have a printed card that works digitally?
Yes. You can print the invitation's QR onto your own paper cards to hand out. The guest scans or opens that code and reaches the live page, so the physical card carries the digital reply and check-in without being cut off from them.
What does a link page do that a card and a PDF cannot?
Three things, all after sending: it collects replies as data against names, it updates details for every guest at once when the plan changes, and it recognises someone at the door through the QR already in their invite. A card or an exported PDF is fixed the moment it leaves you.