Exception while batch processing document with Google Cloud DocumentAI V1 - StatusCode="DeadlineExceeded"

I am trying to create PoC for Google Cloud DocumentAI V1 using this

I am using DocAI to convert .pdf files into text using DocAI BatchProcessing. I have created console application with below code, which is working fine with single document. But when I try to process multiple pdf documents it's throwing exception,

Grpc.Core.RpcException: 'Status(StatusCode="DeadlineExceeded", Detail="Deadline Exceeded", DebugException="Grpc.Core.Internal.CoreErrorDetailException: {"created":"@1650465671.748000000","description":"Deadline Exceeded","file":"......\src\core\ext\filters\deadline\deadline_filter.cc","file_line":81,"grpc_status":4}")'

    public static class DocAIBatchProcess
    {
    const string projectId = "PROJECTID"; 
    const string processorId = "PROCESSID";
    const string location = "us";
    const string gcsInputBucketName = "BUCKETNAME";
    const string gcsOutputBucketName = "gs://BUCKETNAME/OUTPUTFOLDER/";
    const string gcsOutputUriPrefix = "PREFIX";
    const string prefix = "INPUTFOLDER/";
    const string delimiter = "/";

public static bool BatchProcessDocument(this IEnumerable<GCPStorage.Object> storageObjects)
{
        Console.WriteLine("\n");
        Console.WriteLine("Processing documents started...");
        Console.WriteLine("-------------------------------");

        DocumentProcessorServiceClient documentProcessorServiceClient = DocumentProcessorServiceClient.Create();
        string name = $"projects/{projectId}/locations/{location}/processors/{processorId}";

        GcsDocument gcsDocument = null;
        GcsDocuments gcsDocuments = new GcsDocuments();
        var storage = StorageClient.Create();
        foreach (var storageObject in storageObjects)
        {
            if (storageObject.Name != prefix)
            {
                gcsDocument = new GcsDocument()
                {
                    GcsUri = $"gs://gcsInputBucketName/{storageObject.Name}",
                    MimeType = "application/pdf"
                };
                gcsDocuments.Documents.Add(gcsDocument);
            }
        }

        //Input Config
        BatchDocumentsInputConfig inputConfig = new BatchDocumentsInputConfig();
        inputConfig.GcsDocuments = gcsDocuments;

        //Output Config
        var fullGcsPath = $"gs://{gcsOutputBucketName}/{gcsOutputUriPrefix}/";
        GcsOutputConfig gcsOutputConfig = new GcsOutputConfig();
        gcsOutputConfig.GcsUri = gcsOutputBucketName;

        DocumentOutputConfig documentOutputConfig = new DocumentOutputConfig();
        documentOutputConfig.GcsOutputConfig = gcsOutputConfig;

        // Configure the batch process request.
        BatchProcessRequest batchProcessRequest = new BatchProcessRequest();
        batchProcessRequest.Name = name;
        batchProcessRequest.InputDocuments = inputConfig;
        batchProcessRequest.DocumentOutputConfig = documentOutputConfig;

        // Make the request
        Operation<BatchProcessResponse, BatchProcessMetadata> response = documentProcessorServiceClient.BatchProcessDocuments(batchProcessRequest);                
        // Poll until the returned long-running operation is complete
        Operation<BatchProcessResponse, BatchProcessMetadata> completedResponse = response.PollUntilCompleted();
        
        // Retrieve the operation result
        BatchProcessResponse result = completedResponse.Result;
}
}

DeadlineExceeded : "Deadline expired before operation could complete."

I tried looking into documentation but couldn't find anything concreate. If someone knows about why this is happening ? Any assistance would be greatly appreciated.