How to change the page order of PDF files?

this will get you started: split the document (menu document > split); set max pages = 1; now you have myfile_part1, myfile_part2, and so on (each part is a single page); next, create a new pdf from the various parts: combine > merge into single pdf > add files > select the files; arrange by name (move up or down as needed); click combine. note: there are variations on this procedure; you'll need to experiment and teach youself.

Thank you very miuch.
But is there a less tedious solution as there are more than a thousand pages and several pdf files(books)

as far as i know, there is not a way to do this with a convenient tool built into acrobat. using the split document method, it's easy to combine the files in reverse order, if you can rename the individual files such that you have, for example, paage001, page002, ... , page 020, ... ,page030, ... , page100, ... , page999. in the combine dialog you simply click on the 'name' bar to sort the icons in order of 999to001 (as opposed to 001to999). the difficulty is in renaming the files. i think there are file renaming tools available. i use my own techniques and scripts to rename, for example, 'page1' to 'page001', 'page20' to 'page020', etc. so, i can do any number of pages rather efficiently. short of renaming page files, you can use a logical method for reordering the pages using the split/combine technique. say you have a document of 800 pages. first break it in two parts of 400 pages each. add 100 dummy pages (from any source) to each part. focusing on part1, part1 will have 500 pages (100 dummy pages followed by 400 original document pages). split part1 as previously described. delete pages 1 thru 100 (the dummies). you are left with 400 pages numbered page101 ... page500. (key: each page's file name has three digits in the numerical part, so they sort properly in the combine dialog without manual adjusting) combine the 400 pages in reverse order. this segment will be the new part2. repeat the process with original part2 set of 400 pages; this becomes the new part1. last step is to insert the new part2 after the last page of the new part1.

Run this from the JavaScript Console (Ctrl+J):

for (i = this.numPages - 1; i >= 0; i--) this.movePage(i);