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PDF page reordering with itext

I am using the itext pdf library. can anyone know how i can move pages in an existing pdf?

Actually, I want to move the last few pages at the beginning of the file.

This is something like below, but I don't understand how it works.

reader = new PdfReader(baos.toByteArray()); n = reader.getNumberOfPages(); reader.selectPages(String.format("%d, 1-%d", n, n-1)); PdfStamper stamper = new PdfStamper(reader, new FileOutputStream(filename)); stamper.close();

Can someone explain in detail?

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The selectPages() method is explained in chapter 6 of my book (see page 164). In the context of code snippets 6.3 and 6.11, it is used to reduce the number of PdfReader pages PdfReader for consumption by PdfStamper or PdfCopy . However, it can also be used to reorder pages. Let me explain the syntax first.

There are various options for the selectPages() method:

You can pass a List<Integer> containing all the page numbers you want to keep. This list may consist of increasing page numbers, 1, 2, 3, 4, ... If you change the order, for example: 1, 3, 2, 4, ... PdfReader will serve pages with a changed order.

You can also pass a string (this is what is done in your fragment) using the following syntax:

 [!][o][odd][e][even]start[-end]

You can have multiple ranges separated by commas, and! the modifier removes pages from what is already selected. Range changes are incremental; numbers are added or deleted as a range appears. The beginning or end can be omitted; if you omit you need at least o (odd, selects all odd pages) or e (even, selects all even pages).

In your case, we have:

 String.format("%d, 1-%d", n, n-1)

Suppose we have a document with 10 pages, then n is 10, and the result of the formatting operation is "10, 1-9" . In this case, PdfReader will display the last page as the first, and then pages 1 through 9.

Now suppose you have a TOC that starts on page 8 and you want to move this TOC to the first pages, then you need something like this: 8-10, 1-7 , or if toc is 8 and n equal to 10:

 String.format("%d-%d, 1-%d", toc, n, toc -1)

For more information on the format() method, see the API docs for String and String Formatting Syntax .

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