How to merge multiple PDF documents into one

Introduction

In this tutorial, we will look at how to merge multiple PDF documents into one.
We will be using PassportPDF API and C#.

You should have your machine already set up using instructions from our getting started guide.

Merging PDF files using PassportPDF

To merge multiple PDF documents into one, we will use the following endpoints:

• DocumentLoadFromURIAsync to load a document from a URI.
• MergeAsync to merge the different PDF files into one.
• SaveDocumentAsync to download the final merged document.

These endpoints are shown in the following example:

using PassportPDF.Api;
using PassportPDF.Client;
using PassportPDF.Model;
 
namespace PdfMerger
{
 
    public class PdfMerger
    {
        static async Task Main(string[] args)
        {
            GlobalConfiguration.ApiKey = "YOUR-PASSPORT-CODE";
 
            PassportManagerApi apiManager = new();
            PassportPDFPassport passportData = await apiManager.PassportManagerGetPassportInfoAsync(GlobalConfiguration.ApiKey);
 
            if (passportData == null)
            {
                throw new ApiException("The Passport number given is invalid, please set a valid passport number and try again.");
            }
            else if (passportData.IsActive is false)
            {
                throw new ApiException("The Passport number given not active, please go to your PassportPDF dashboard and active your plan.");
            }
 
            string uri1 = "https://passportpdfapi.com/test/invoice_with_barcode.pdf";
            string uri2 = "https://passportpdfapi.com/test/multiple_pages.pdf";
 
            List<string> uriList = new List<string> {uri1, uri2};
 
            DocumentApi docApi = new();
 
            Console.WriteLine("Loading documents into PassportPDF...");
 
            List<string> listOfFilesIds = new List<string>();
 
            foreach (string uri in uriList)
            {
                DocumentLoadResponse document = await docApi.DocumentLoadFromURIAsync(new LoadDocumentFromURIParameters(uri));
                string uriId = document.FileId;
                listOfFilesIds.Add(uriId);
            }
 
            Console.WriteLine("Documents loaded.");
 
            Console.WriteLine("Merging PDF documents..");
 
            PDFApi pdfApi = new();
 
            PdfMergeResponse pdfMergeResponse = await pdfApi.MergeAsync(new PdfMergeParameters(listOfFilesIds));
 
            if (pdfMergeResponse.Error is not null)
            {
                throw new ApiException(pdfMergeResponse.Error.ExtResultMessage);
            }
            else
            {
                Console.WriteLine("PDF documents have been successfully merged.");
            }
 
            // Download merged document
            Console.WriteLine("Downloading merged document..");
            try
            {
                string mergedDocumentId = pdfMergeResponse.FileId;
 
                string savePath = Path.Join(Directory.GetCurrentDirectory(), "merged_document.pdf");
 
                PdfSaveDocumentResponse pdfSaveDocumentResponse = await pdfApi.SaveDocumentAsync(new PdfSaveDocumentParameters(mergedDocumentId));
 
                File.WriteAllBytes(savePath, pdfSaveDocumentResponse.Data);
 
                if (pdfMergeResponse.Error is not null)
                {
                    throw new ApiException(pdfSaveDocumentResponse.Error.ExtResultMessage);
                }
                else
                {
                    Console.WriteLine("Merged document has been successfully downloaded. It has been saved in : {0}", savePath);
                }
 
            }
            catch (Exception ex)
            {
                Console.WriteLine("Could not download merged document! : {0}", ex.Message);
            }
 
        }
    }
}

For the complete .NET project, please visit the GitHub repo of this tutorial.

Although this example shows how to merge only two documents, you can easily generalize it to merge many more documents.

You just need to specify the URIs of your other documents and then add them to the list of URIs that will be then passed to the MergeAsync endpoint.

Final remarks

The documents will be merged in the same order as the order of file IDs that are passed to the MergeAsync endpoint.

For more information regarding the use of this endpoint, as well as other PassportPDF endpoints, please visit the API reference page.