PM> Install-Package Spire.PDF

using Spire.Pdf;
using Spire.Pdf.Fields;
using Spire.Pdf.Widget;
using System.IO;
using System.Text;

namespace ExtractFormFieldValues
{
    internal class Program
    {
        static void Main(string[] args)
        {            
            //Initialize an instance of the PdfDocument instance
            PdfDocument doc = new PdfDocument();
            //Load a PDF document
            doc.LoadFromFile(@"Forms.pdf");

            //Initialize an instance of the StringBuilder class
            StringBuilder sb = new StringBuilder();

            //Get the form from the document
            PdfFormWidget formWidget = doc.Form as PdfFormWidget;

            //Iterate through all fields in the form
            for (int i = 0; i < formWidget.FieldsWidget.List.Count; i++)
            {
                PdfField field = formWidget.FieldsWidget.List[i] as PdfField;

                //Get the name and value of textbox field
                if (field is PdfTextBoxFieldWidget)
                {
                    PdfTextBoxFieldWidget textBoxField = field as PdfTextBoxFieldWidget;                    
                    string name = textBoxField.Name;
                    string value = textBoxField.Text;
                    sb.Append("Textbox Name: " + name + "\r\n");
                    sb.Append("Textbox Value: " + value + "\r\n");
                }

                //Get the name, items and selected item of list box field
                if (field is PdfListBoxWidgetFieldWidget)
                {
                    PdfListBoxWidgetFieldWidget listBoxField = field as PdfListBoxWidgetFieldWidget;
                    string name = listBoxField.Name;
                    sb.Append("Listbox Name: " + name + "\r\n");
                    sb.Append("Listbox Items: \r\n");

                    PdfListWidgetItemCollection items = listBoxField.Values;

                    foreach (PdfListWidgetItem item in items)
                    {
                        sb.Append(item.Value + "\r\n");
                    }
                    string selectedValue = listBoxField.SelectedValue;
                    sb.Append("Listbox Selected Value: " + selectedValue + "\r\n");
                }

                //Get the name, items and selected item of combo box field
                if (field is PdfComboBoxWidgetFieldWidget)
                {
                    PdfComboBoxWidgetFieldWidget comBoxField = field as PdfComboBoxWidgetFieldWidget;
                    string name = comBoxField.Name;
                    sb.Append("Combobox Name: " + name + "\r\n");
                    sb.Append("Combobox Items: \r\n");
                    PdfListWidgetItemCollection items = comBoxField.Values;

                    foreach (PdfListWidgetItem item in items)
                    {
                        sb.Append(item.Value + "\r\n");
                    }
                    string selectedValue = comBoxField.SelectedValue;
                    sb.Append("Combobox Selected Value: " + selectedValue + "\r\n");

                }

                //Get the name and selected item of radio button field
                if (field is PdfRadioButtonListFieldWidget)
                {
                    PdfRadioButtonListFieldWidget radioBtnField = field as PdfRadioButtonListFieldWidget;
                    string name = radioBtnField.Name;
                    sb.Append("Radio Button Name: " + name + "\r\n");
                    string selectedValue = radioBtnField.SelectedValue;
                    sb.Append("Radio Button Selected Value: " + selectedValue + "\r\n");
                }

                //Get the name and status of checkbox field
                if (field is PdfCheckBoxWidgetFieldWidget)
                {
                    PdfCheckBoxWidgetFieldWidget checkBoxField = field as PdfCheckBoxWidgetFieldWidget;
                    string name = checkBoxField.Name;
                    sb.Append("Checkbox Name: " + name + "\r\n");
                    bool status = checkBoxField.Checked;
                    if (status)
                    {
                        sb.Append("Checkbox Status: Checked \r\n");
                    }
                    else
                    {
                        sb.Append("Checkbox Status: Unchecked \r\n");
                    }
                }

                sb.Append("\n");
            }

            //Write the content of the StringBuilder into a text file
            File.WriteAllText("GetAllValues.txt", sb.ToString());
            doc.Dispose();
        }
    }
}

Imports Spire.Pdf
Imports Spire.Pdf.Fields
Imports Spire.Pdf.Widget
Imports System.IO
Imports System.Text

Namespace ExtractFormFieldValues
    Friend Class Program
        Private Shared Sub Main(ByVal args As String())
            'Initialize an instance of the PdfDocument instance
            Dim doc As PdfDocument = New PdfDocument()
            'Load a PDF document
            doc.LoadFromFile("Forms.pdf")

            'Initialize an instance of the StringBuilder class
            Dim sb As StringBuilder = New StringBuilder()

            'Get the form from the document
            Dim formWidget As PdfFormWidget = TryCast(doc.Form, PdfFormWidget)

            'Iterate through all fields in the form
            For i As Integer = 0 To formWidget.FieldsWidget.List.Count - 1
                Dim field As PdfField = TryCast(formWidget.FieldsWidget.List(i), PdfField)

                'Get the name and value of textbox field
                If TypeOf field Is PdfTextBoxFieldWidget Then
                    Dim textBoxField As PdfTextBoxFieldWidget = TryCast(field, PdfTextBoxFieldWidget)
                    Dim name As String = textBoxField.Name
                    Dim value As String = textBoxField.Text
                    sb.Append("Textbox Name: " & name & vbCrLf)
                    sb.Append("Textbox Value: " & value & vbCrLf)
                End If

                'Get the name, items and selected item of list box field
                If TypeOf field Is PdfListBoxWidgetFieldWidget Then
                    Dim listBoxField As PdfListBoxWidgetFieldWidget = TryCast(field, PdfListBoxWidgetFieldWidget)
                    Dim name As String = listBoxField.Name
                    sb.Append("Listbox Name: " & name & vbCrLf)
                    sb.Append("Listbox Items: " & vbCrLf)

                    Dim items As PdfListWidgetItemCollection = listBoxField.Values

                    For Each item As PdfListWidgetItem In items
                        sb.Append(item.Value.ToString() & vbCrLf)
                    Next
                    Dim selectedValue As String = listBoxField.SelectedValue
                    sb.Append("Listbox Selected Value: " & selectedValue & vbCrLf)
                End If

                'Get the name, items and selected item of combo box field
                If TypeOf field Is PdfComboBoxWidgetFieldWidget Then
                    Dim comBoxField As PdfComboBoxWidgetFieldWidget = TryCast(field, PdfComboBoxWidgetFieldWidget)
                    Dim name As String = comBoxField.Name
                    sb.Append("Combobox Name: " & name & vbCrLf)
                    sb.Append("Combobox Items: " & vbCrLf)
                    Dim items As PdfListWidgetItemCollection = comBoxField.Values

                    For Each item As PdfListWidgetItem In items
                        sb.Append(item.Value.ToString() & vbCrLf)
                    Next
                    Dim selectedValue As String = comBoxField.SelectedValue
                    sb.Append("Combobox Selected Value: " & selectedValue & vbCrLf)

                End If

                'Get the name and selected item of radio button field
                If TypeOf field Is PdfRadioButtonListFieldWidget Then
                    Dim radioBtnField As PdfRadioButtonListFieldWidget = TryCast(field, PdfRadioButtonListFieldWidget)
                    Dim name As String = radioBtnField.Name
                    sb.Append("Radio Button Name: " & name & vbCrLf)
                    Dim selectedValue As String = radioBtnField.SelectedValue
                    sb.Append("Radio Button Selected Value: " & selectedValue & vbCrLf)
                End If

                'Get the name and status of checkbox field
                If TypeOf field Is PdfCheckBoxWidgetFieldWidget Then
                    Dim checkBoxField As PdfCheckBoxWidgetFieldWidget = TryCast(field, PdfCheckBoxWidgetFieldWidget)
                    Dim name As String = checkBoxField.Name
                    sb.Append("Checkbox Name: " & name & vbCrLf)
                    Dim status As Boolean = checkBoxField.Checked
                    If status Then
                        sb.Append("Checkbox Status: Checked " & vbCrLf)
                    Else
                        sb.Append("Checkbox Status: Unchecked " & vbCrLf)
                    End If
                End If

                sb.Append(vbLf)
            Next

            'Write the content of the StringBuilder into a text file
            Call File.WriteAllText("GetAllValues.txt", sb.ToString())
            doc.Dispose()
        End Sub
    End Class
End Namespace