Some pages show only a number instead of a thumbnail. Will they be lost when I export?

Thumbnails are for display only

The reorder tool has two completely separate stages. The first is display: your browser draws a small picture of each page so you can see it and decide where it goes. The second is export: the tool takes your original file and rewrites its list of pages in the sequence you chose, without touching any page's content and without using the thumbnails at all. So a thumbnail that fails to draw has no effect on the real page.

Why some pages will not draw

• A page with a very large image or complex artwork that is more than the browser can render quickly, especially on a phone.
• A font or element in a format the browser's renderer does not support, while a desktop PDF program shows it without trouble.
• Memory pressure on the device with a big file, so rendering stops for some pages.

When this happens you see a message: some thumbnails could not be rendered, you can still reorder and export the pages. The page stays in the grid with its box, its number and its four buttons.

Working with a page that has no picture

1. In Reorder PDF pages, note the page label under its box, such as Page 12. That is its number in the original file.
2. Open the original in a PDF reader on your device and go to page 12 to see what is on it.
3. Come back to the tool and move the page with its buttons like any other.
4. Check its place in the “New order” line, where 12 appears in its new position.
5. Press “Download in new order”, then open the output in the same reader and confirm the page is there and intact.

When to actually worry

If no thumbnail draws at all and an error appears when you open the file, the file may be damaged or protected. Password-protected or encrypted files are refused from the start, and the tool never bypasses protection. One or two pages without a picture in a file that otherwise displayed normally is just a display matter.