Updating PDF page

[LuisHer27]

Describe the bug

• I'm trying to add a signature in the last page of the pdf and I want put the signature at the bottom of the page. But it seems like I'm not able to achieve it. The text looks flipped and I can't manipulate the blue container location.

To Reproduce
Code snippet to reproduce the behavior:

Future<File> getFile() async {
  final data = await rootBundle.load('assets/participant_agreement.pdf');
  final bytes = data.buffer.asUint8List();
  final dir = await getApplicationDocumentsDirectory();
  final file = File('${dir.path}/form.pdf');

  final assetFile = await file.writeAsBytes(bytes);

  return assetFile;
}

class PdfEditorService {
  const PdfEditorService._();

  static Future<File> addSignatureToPDF(Uint8List signature) async {
    try {
      final font = await PdfGoogleFonts.nunitoExtraLight();

      final file = await getFile();
      final form = file.readAsBytesSync();

      final image = MemoryImage(signature);

      final document = PdfDocumentParser(
        form,
      );

      final lastPage = document.pages.length - 1;

      final themePage = PageTheme(
        pageFormat: PdfPageFormat.a4,
        buildBackground: (context) {
          return Container(color: PdfColors.blue);
        },
      );

      final pdf = Document.load(document)
        ..editPage(
          lastPage,
          Page(
            pageTheme: themePage,
            build: (context) {
              return Column(
                children: [
                  Text(
                    'Participant Agreement Form',
                    style: TextStyle(
                      font: font,
                      fontSize: 32,
                    ),
                  ),
                  SizedBox(height: 12),
                  Text(
                    'Name: Anakin Skywalker',
                    style: TextStyle(
                      font: font,
                      fontSize: 32,
                    ),
                  ),
                  Positioned(
                    top: 0,
                    left: 0,
                    child: Column(
                      children: [
                        Text(
                          'Signature',
                          style: TextStyle(
                            font: font,
                            fontSize: 32,
                          ),
                        ),
                        SizedBox(height: 20),
                        Image(image),
                        SizedBox(height: 8),
                        Container(
                          height: 1,
                          width: 200,
                          decoration: BoxDecoration(
                            border: Border.all(),
                          ),
                        ),
                        SizedBox(height: 10),
                        Text(
                          'Date: 2021-09-01',
                          style: TextStyle(
                            font: font,
                            fontSize: 32,
                          ),
                        ),
                      ],
                    ),
                  )
                ],
              );
            },
          ),
        );

      final dir = await getApplicationDocumentsDirectory();
      final signedForm = File('${dir.path}/form.pdf');
      return await signedForm.writeAsBytes(await pdf.save());
    } catch (e) {
      log(e.toString());
      throw Exception('Error adding signature to PDF');
    }
  }
}

Expected
expected_behavior.pdf
behavior

Screenshots

Flutter Doctor

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[✓] Connected device (5 available)
    • sdk gphone64 arm64 (mobile) • emulator-5556             • android-arm64  • Android 14 (API 34) (emulator)
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Desktop (please complete the following information):

• iOS
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Smartphone (please complete the following information):

• Device: [iPhone 14]
• OS: [Pixel 8]
• Version [e.g. 22]

Additional context