What the app does not do (yet)

Said plainly, because a greyed button with no explanation is worse than a missing one:

Password protection / encryption — the welcome tile says "not available in this build", and it means it.
Adding or deleting pages — removed on purpose. You can reorder, rotate, duplicate and extract pages and merge another PDF in, but not add a blank page or delete one.
Reshaping page objects — you can move, resize and reorder what is on a page, but not edit its outline point by point, group things together, lock them, or combine shapes.
Gradients and patterns on page objects — you can change a solid colour, not fill an object with a gradient or a pattern.
Re-flowing text — a PDF page has no paragraphs, so changing alignment, line spacing or case is not possible. (The typeface, size and colour of printed text can be changed — see §4 — but the words stay where the page put them.)
Exporting a page as SVG — removed; export to PDF, PNG, JPEG, TIFF or Word instead.