What it does

Merges two or more PDF documents into a single PDF file. The order of the pages follows the alphabetical order of the input file names.

Inputs and limits

Input: PDF files.
Minimum: two PDF files.
No explicit size limit is documented; the operation runs in memory and may be limited by the host system.

Web app

The page asks you to select PDF files, optionally reorder them, and click MERGE. It then combines the selected files and provides a single merged PDF for download. (Source: UI text shows “Combine PDF files in any order.”)

Command line (CLI)

The Documentize.Merge plugin merges PDF files placed in a task‑specific input folder and writes the merged result to a matching output folder. Provide a task ID to identify the folders.

# Linux / macOS (needs the .NET 10 runtime and documentize.lic next to the DLL)
export PLUGIN_INPUT_DIR=./work/input
export PLUGIN_OUTPUT_DIR=./work/output
mkdir -p "$PLUGIN_INPUT_DIR/job1"
cp sample.pdf cv.pdf "$PLUGIN_INPUT_DIR/job1/"
dotnet Documentize.Merge.dll --task-id job1
ls "$PLUGIN_OUTPUT_DIR/job1"

# Windows PowerShell
$env:PLUGIN_INPUT_DIR  = "$PWD\work\input"
$env:PLUGIN_OUTPUT_DIR = "$PWD\work\output"
New-Item -ItemType Directory -Force "$env:PLUGIN_INPUT_DIR\job1" | Out-Null
Copy-Item sample.pdf, cv.pdf "$env:PLUGIN_INPUT_DIR\job1\"
dotnet Documentize.Merge.dll --task-id job1
Get-ChildItem "$env:PLUGIN_OUTPUT_DIR\job1"

Documentize.Plugins (C#)

The Documentize.Plugins library offers a MergeOptions object. Add each input PDF with options.AddInput(new FileData(file)), specify the output file with options.AddOutput(new FileData(...)), and call PdfManager.Merge(options). A license file documentize.lic must be present.

#:package Documentize@26.9.0

using Documentize;

// Apply the license file placed next to the program, then merge every PDF of the input folder in filename order.
License.Set("documentize.lic");

var inputDir = args[0];
var outputDir = args[1];

var options = new MergeOptions();
foreach (var file in Directory.GetFiles(inputDir, "*.pdf").OrderBy(f => f, StringComparer.Ordinal))
{
    options.AddInput(new FileData(file));
}
options.AddOutput(new FileData(Path.Combine(outputDir, "merged.pdf")));

PdfManager.Merge(options);
Console.WriteLine("merged.pdf written");

Save it as app.cs and run dotnet run app.cs -- ./in ./out (.NET 10 SDK).

Aspose.PDF.FOSS (C#)

Using Aspose.PDF.FOSS, load all PDF files from the input folder, order them alphabetically, and call new PdfFileEditor().Concatenate(files, outputPath). No license is required.

#:package Aspose.PDF.FOSS@26.11.0

using Aspose.Pdf.Facades;

var inputDir = args[0];
var outputDir = args[1];

var files = Directory.GetFiles(inputDir, "*.pdf").OrderBy(f => f, StringComparer.Ordinal).ToArray();
new PdfFileEditor().Concatenate(files, Path.Combine(outputDir, "merged.pdf"));
Console.WriteLine("merged.pdf written");