public string[] GetPdfUrlsWithinDirectory(ContentFolder parentFolder)
        {
            if (parentFolder == null)
            {
                return(new string[0]);
            }

            try
            {
                var pdfFiles =
                    _contentRepository
                    .GetChildren <PdfFile>(
                        GetFolderReference(parentFolder));

                return(pdfFiles.Select(pdfFile => _linkResolver.GetFriendlyUrl(pdfFile.ContentLink)).ToArray());
            }
            catch (Exception e)
            {
                Log.Error($"Could not retrieve Pdf file Urls from {parentFolder.RouteSegment}", e);
            }

            return(new string[0]);
        }