PDF Indexes and Multisearchers

If you want to index PDF files and search for them, you will need to use the UmbracoExamine.Pdf extension package.

Installation

Install with NuGet:dotnet add package Umbraco.ExaminePDF

Installing the package creates a new Examine index called PDFIndex, which appears in the Examine Management dashboard under the Settings section. This index extracts and indexes the text content of PDF files uploaded to the Media section, not their filenames.

PDFIndex index under Examine Management section

To get results, search for words that appear inside the PDF. Scanned or image-based PDFs have no extractable text and will return no results.

PDFIndex Search Results

Multi-index searchers

A multi-index searcher is a searcher that can search multiple indexes. The multi-index searcher can be helpful when you want to search both the external and internal indexes.

You can register a multi-index searcher with the ExamineManager on startup:

using Examine;
using Umbraco.Cms.Core;
using Umbraco.Cms.Core.Composing;
using Umbraco.Cms.Core.DependencyInjection;
using UmbracoExamine.PDF;

namespace MySite.MyCustomIndex;

[ComposeAfter(typeof(ExaminePdfComposer))]
public class ExamineComposer : IComposer
{
    public void Compose(IUmbracoBuilder builder)
    {
        builder.Services.AddExamineLuceneMultiSearcher("MultiSearcher", new[] {Constants.UmbracoIndexes.ExternalIndexName, PdfIndexConstants.PdfIndexName});
    }
}

With this approach, the multi-index searcher will show up in the Examine Management dashboard.

MultiSearcher Search in the "Examine Management" dashboard

The multi-index searcher can be resolved in code from the ExamineManager:

if (_examineManager.TryGetSearcher("MultiSearcher", out var searcher))
{
    //TODO: use the `searcher` to search
}

The implementation of IPdfTextExtractor is PdfSharpTextExtractor in this library, which uses PDFSharp to extract the bytes to convert to text. The implementation does not deal well with Unicode text, which means when some PDF files are read, the result will be 'junk' strings.

You can replace the IPdfTextExtractor using your own composer:

composition.RegisterUnique<IPdfTextExtractor, MyCustomSharpTextExtractor>();

The iTextSharp library deals with Unicode in a better way but is a paid license. If you wish to use iTextSharp or another PDF library, you can swap out the IPdfTextExtractor with your own implementation.