Fixes fill form guide

fern/pages/help_center/pdf-forms/fill.mdx

@@ -15,84 +15,91 @@ Ensure you have the following:
 
 ### Prepare the form data as a list of object as follows
 
+Note: if you don't know what the field names are, you should use the [mark form fields](/help_center/pdf-forms/mark) or [detect form fields](/help_center/pdf-forms/fill) API endpoints to get the field names.
+
+Here are the most common fields and supported types:
+
+| Field Type      | Options            |
+| --------------- | ------------------ |
+| PDFTextField    | `value: string`    |
+| PDFOptionList   | `selected: string` |
+| PDFDropdownList | `selected: string` |
+| PDFCheckBox     | `checked: boolean` |
+| PDFRadioGroup   | `selected: string` |
+
 ```typescript
 [
-    {
-        name: "Producer Name",
-        type: "PDFTextField",
-        value: "Titouan Launay", // fills a text field
-    },
-    {
-        name: "Check Box4",
-        type: "PDFCheckBox",
-        checked: false, // unchecks a box
-    },
-]
+  {
+    name: "Producer Name",
+    type: "PDFTextField",
+    value: "Titouan Launay", // fills a text field
+  },
+  {
+    name: "Check Box4",
+    type: "PDFCheckBox",
+    checked: false, // unchecks a box
+  },
+];
 ```
 
-### Mark form fields from the PDF and retrieve a modified PDF
+### Fill form fields from the PDF and retrieve a modified PDF
 
 ```typescript
 import { FileforgeClient } from "@fileforge/client";
 import * as fs from "fs";
-import { pipeline } from 'stream';
-import { promisify } from 'util';
+import { pipeline } from "stream";
+import { promisify } from "util";
 
 const pipelineAsync = promisify(pipeline);
 
 (async () => {
-    const ff = new FileforgeClient({
-      apiKey: process.env.FILEFORGE_API_KEY,
-    });
-
-    try {
-      const formFillRequest = {
-        options: {
-          fields: [
-            {
-              name: "Producer Name",
-              type: "PDFTextField",
-              value: "Pierre Dorge"
-            },
-            {
-                name:"Check Box4",
-                type:"PDFCheckBox",
-                checked: false
-            },
-          ],
-        },
-      };
-      const requestOptions = {
-        timeoutInSeconds: 60,
-        maxRetries: 3,
-      };
-      const filledPdfStream = await ff.pdf.form.fill(
-        new File(
-          [fs.readFileSync(__dirname + "/form.pdf")],
-          "form.pdf",
+  const ff = new FileforgeClient({
+    apiKey: process.env.FILEFORGE_API_KEY,
+  });
+
+  try {
+    const formFillRequest = {
+      options: {
+        fields: [
           {
-            type: "application/pdf",
+            name: "Producer Name",
+            type: "PDFTextField",
+            value: "Pierre Dorge",
           },
-        ),
-        formFillRequest,
-        requestOptions,
-      );
-
-
-      await pipelineAsync(filledPdfStream, fs.createWriteStream("./result_filled.pdf")); // ensures the whole file is written before the stream is closed
-
-      console.log("PDF form filling successful. Stream ready.");
-    } catch (error) {
-      console.error("Error during PDF form filling:", error);
-    }
-  })();
+          {
+            name: "Check Box4",
+            type: "PDFCheckBox",
+            checked: false,
+          },
+        ],
+      },
+    };
+    const requestOptions = {
+      timeoutInSeconds: 60,
+      maxRetries: 3,
+    };
+    const filledPdfStream = await ff.pdf.form.fill(
+      new File([fs.readFileSync(__dirname + "/form.pdf")], "form.pdf", {
+        type: "application/pdf",
+      }),
+      formFillRequest,
+      requestOptions
+    );
+
+    await pipelineAsync(
+      filledPdfStream,
+      fs.createWriteStream("./result_filled.pdf")
+    ); // ensures the whole file is written before the stream is closed
+
+    console.log("PDF form filling successful. Stream ready.");
+  } catch (error) {
+    console.error("Error during PDF form filling:", error);
+  }
+})();
 ```
 
 ### Get a modified PDF
-The reponse is stream of the modified PDF with form fields marked with a green border, and hover text showing the field name.
-
-![sample marked pdf file](../../../assets/form-pdf-marked.png)
-
 
+The reponse is stream of the filled PDF document.
 
-</Steps>
+</Steps>