PDF to long image

Do any one of the three things it suggests: drop sharpness from 2x or 1.5x to 1x (total pixels fall by the square, so this usually passes at once); use the page range to export just the pages you need most first (say 1-5); or split into two long images, first half and second half separately. Forcing an export would only yield a blank picture, which is why this page stops you beforehand.

Chat apps cap image dimensions and weight, and over-long strips get compressed hard - the compression ratio grows with the total height. Two ways out: use fewer pages and cut the strip shorter; or switch to the PDF-to-image page and export page-by-page PNGs (your reader can zoom each one for the small print), or just send the PDF itself.

No. The finished width is the widest of the pages being joined; narrower pages keep their original ratio, centered, with your chosen background colour filling the sides - nothing gets stretched just to fill. Pages of one PDF are usually the same width, so most of the time there is no banding at all.

No. The long image is a bitmap: the page's text becomes pixels, and both copying and searching are gone. If the text must stay usable, send the original PDF - the long strip is for a quick glance, not a searchable archive.

A PDF with an open password cannot be parsed by the browser, so this page cannot handle it either. Open it in a reader, enter the password and save an unencrypted copy, then drop that copy in for stitching. Your original file is never modified, and choosing another file clears the in-memory copy.