PDF Document Manipulation in Java

Aspose.PDF FOSS for Java provides a rich set of APIs for manipulating existing PDF documents — splitting, concatenating, extracting pages, inserting page ranges, and resizing content within pages. These capabilities are concentrated in PdfFileEditor and its companion classes ContentsResizeParameters and ContentsResizeValue.

PdfFileEditor: Core Page Operations

The PdfFileEditor class is the central facility for high-level PDF file operations. It provides methods for concatenating multiple PDF files, extracting page subsets, splitting a document into individual pages, and inserting pages from one document into another at a specific position.

PdfFileEditor editor = new PdfFileEditor();
// Concatenate two documents into one
editor.concatenate("first.pdf", "second.pdf", "combined.pdf");
// Extract pages 2 through 5 to a new file
editor.extract("source.pdf", 2, 5, "extracted.pdf");

Key methods include:

  • concatenate(inputFiles, outputFile) — merges multiple documents in order
  • extract(inputFile, startPage, endPage, outputFile) — exports a contiguous range
  • extract(inputFile, pageNumbers, outputFile) — exports a non-contiguous set
  • splitToPages(inputFile) — splits into one ByteArrayOutputStream per page
  • insert(inputFile, insertPosition, portFile, startPage, endPage, outputFile) — inserts a range
  • delete(inputFile, pageNumbers, outputFile) — removes specific pages
  • append(inputFile, portFile, startPage, endPage, outputFile) — appends a page range

For large files, setUseDiskBuffer(true) switches internal storage from heap to disk.

Content Resizing with ContentsResizeParameters

PdfFileEditor.resizeContents() adjusts content within existing page boundaries. Each margin — left, right, top, bottom — and the content width and height are specified as ContentsResizeValue instances, constructed via the factory methods ContentsResizeValue.percents(value) or ContentsResizeValue.units(value).

try (Document doc = new Document("input.pdf")) {
    PdfFileEditor editor = new PdfFileEditor();
    ContentsResizeParameters params = new ContentsResizeParameters(
        ContentsResizeValue.percents(10),   // left margin
        ContentsResizeValue.percents(80),   // content width
        ContentsResizeValue.percents(10),   // right margin
        ContentsResizeValue.percents(10),   // top margin
        ContentsResizeValue.percents(80),   // content height
        ContentsResizeValue.percents(10)    // bottom margin
    );
    editor.resizeContents(doc, params);
    doc.save("resized.pdf");
}

The six-argument constructor for ContentsResizeParameters accepts values in the order: leftMargin, contentsWidth, rightMargin, topMargin, contentsHeight, bottomMargin. All six must sum to 100% when using percentage-based values, or match the page dimensions when using absolute point values.

Resizing Specific Pages

When only a subset of pages requires resizing, the overload that accepts an integer array of page numbers targets those pages while leaving the rest unchanged:

PdfFileEditor editor = new PdfFileEditor();
ContentsResizeParameters params = new ContentsResizeParameters(
    ContentsResizeValue.units(28),   // left margin in points
    ContentsResizeValue.units(540),  // content width
    ContentsResizeValue.units(28),   // right margin
    ContentsResizeValue.units(28),   // top margin
    ContentsResizeValue.units(786),  // content height
    ContentsResizeValue.units(28)    // bottom margin
);
// Only resize pages 1 and 3
editor.resizeContents(doc, new int[]{1, 3}, params);

ContentsResizeValue.getValue() and isPercent() allow inspecting the stored value and determining whether it represents a percentage or an absolute point count.

Booklet and N-Up Layout

PdfFileEditor includes makeBooklet() for imposing pages in two-sided booklet order and makeNUp() for tiling multiple pages per sheet. Both methods accept file paths or streams:

PdfFileEditor editor = new PdfFileEditor();
// Print as a folded booklet
editor.makeBooklet("input.pdf", "booklet.pdf");
// Tile 2 columns × 3 rows per sheet
editor.makeNUp("input.pdf", "nup.pdf", 2, 3);

PdfPageEditor: Per-Page Zoom Control

PdfPageEditor targets individual page properties such as zoom level. setZoom() accepts a float multiplier that controls the initial magnification when the document is opened in a viewer:

PdfPageEditor pageEditor = new PdfPageEditor();
pageEditor.bindPdf("input.pdf");
pageEditor.setZoom(1.5f);
pageEditor.save("zoomed.pdf");

Values of 0.0 or negative are rejected — getZoom() returns 1.0 in those cases. This makes PdfPageEditor suitable for preparing documents that must open at a specific magnification for accessibility or kiosk display use cases.

Getting Started

Add the Maven dependency and import the facades package:

<dependency>
  <groupId>org.aspose</groupId>
  <artifactId>aspose-pdf</artifactId>
  <version>0.1.0-alpha</version>
</dependency>

import org.aspose.pdf.*;
import org.aspose.pdf.facades.*;

Aspose.PDF FOSS for Java is MIT-licensed and available at https://github.com/aspose-pdf-foss/Aspose.PDF-FOSS-for-Java.