PPF-524: update docs

docs/install.md

@@ -21,6 +21,10 @@ pip install -U PyPDFForm
 
 ## Create a PDF wrapper
 
+There are two classes provided by the library that abstract a PDF form. The `FormWrapper` class allows you to fill a 
+PDF form if you don't need any other API. More info about `FormWrapper` can be found 
+[here](simple_fill.md).
+
 The class that implements most of PyPDFForm's APIs is `PdfWrapper`. It takes various optional parameters to instantiate, 
 with the most important one being the PDF form "template".
 

docs/simple_fill.md

@@ -1 +1,32 @@
 # Fill a PDF form in place (beta)
+
+**NOTE:** This page contains beta features, meaning it's known that these features do not support some PDF forms but 
+currently there are no plans and/or solutions to fix them.
+
+The `FormWrapper` class allows you to fill a PDF form in place as if you were filling it manually. The resulted filled 
+PDF form will NOT be flattened and will still be editable.
+
+Similar to the `PdfWrapper` class, the `FormWrapper` also supports widgets including text fields, checkboxes, radio 
+buttons, dropdowns, and paragraphs. However, it does NOT support signature widgets.
+
+Consider [this PDF](https://github.com/chinapandaman/PyPDFForm/raw/master/pdf_samples/dropdown/sample_template_with_dropdown.pdf):
+
+```python
+from PyPDFForm import FormWrapper
+
+filled = FormWrapper("sample_template_with_dropdown.pdf").fill(
+    {
+        "test_1": "test_1",
+        "test_2": "test_2",
+        "test_3": "test_3",
+        "check_1": True,
+        "check_2": True,
+        "check_3": True,
+        "radio_1": 1,
+        "dropdown_1": 1,
+    },
+)
+
+with open("output.pdf", "wb+") as output:
+    output.write(filled.read())
+```