Spread that sheet turns a PDF of single pages into the spreads of an open book, as a flatbed scanner would see them: the shadow in the gutter, the pages curving into the binding, the edges of the other pages, the paper.

Free, in the browser at spread-that-sheet.org.

Gutter shadow, with its intensity and width. Margins: the stack of pages at the sides, wider at the start and the end of the book. Page warp near the spine. Paper texture from a library, a solid tint or a scan of your own, lighter on the ink than on the bare paper. Transparency, for thin paper where the back shows through. Covers as single pages, with the boards of a hardcover. Several PDFs merged into one book, with page ranges, and exceptions for chosen pages. A canvas around the spread, coloured or transparent, with a drop shadow. Settings saved and loaded again as a profile. Export as PDF, PNG or JPG at 300 dpi.

The PDF never leaves the computer: everything happens in the browser, nothing is uploaded or collected. No account, no sign-up.