Merging and Page Selection

Merging files

Start with an empty document and chain .merge() calls to append pages from other files:

try (PdfDocument op = PdfDocument.create()) {
    byte[] result = op
        .merge(new File("cover.pdf"))
        .merge(new File("report.pdf"))
        .merge(new File("appendix.pdf"))
        .saveBytes();
}

Selecting pages from a merged file

Every .merge() call accepts an optional page spec that controls which pages get appended:

op.merge(new File("report.pdf"), "1-3")      // pages 1 to 3
op.merge(new File("report.pdf"), "1,4,7")    // specific pages
op.merge(new File("report.pdf"), "2-4,8")    // a range plus individual pages

Page spec syntax

Syntax	What it selects
`"1-5"`	Pages 1 through 5, inclusive
`"1,3,5"`	Specific pages
`"1-3,7"`	A mix of ranges and individual pages
`"3,1"`	Reordering: page 3 first, then page 1

Page numbers are 1-based.

Selecting pages from a loaded document

Use .pages() to filter or reorder the pages of the document you already loaded:

// Keep only pages 1, 3, 4, and 5
try (PdfDocument op = PdfDocument.load(new File("large.pdf"))) {
    byte[] subset = op.pages("1,3-5").saveBytes();
}

// Reverse a 3-page document
op.pages("3,2,1")

Password-protected sources

For encrypted source files, pass the password to .merge():

op.merge(new File("confidential.pdf"), "owner-password", "1-3")

Or load it separately and merge the loaded operation:

try (PdfDocument source = PdfDocument.load(new File("confidential.pdf"), "password");
     PdfDocument result = PdfDocument.create()) {

    result.merge(source, "2-4").save(new File("output.pdf"));
}

Using PageSelection directly

If you prefer not to use a string spec, you can use PageSelection instead:

import pdf.dev.ditsche.kawa.PageSelection;

op.merge(file, PageSelection.of(1, 3, 5))
op.merge(file, PageSelection.range(2, 8))
op.pages(PageSelection.all())