return Stack(
              children: [
                SizedBox(
                  height: MediaQuery.of(context).size.height,
                  width: MediaQuery.of(context).size.width,
                  child: PdfViewer(
                    filePath: snapshot.data!.path,
                  ),
                ),
                if (showThumbnail)
                  Positioned(
                    bottom: 0,
                    width: MediaQuery.of(context).size.width,
                    // Here's the thumbnail widget.
                    child: PdfThumbnail.fromFile(snapshot.data!.path),
                  ),
              ],
            );