...
You will see options for Rich Text Content Control
or Plain Text Content Control 
which allows you to add an accessible text box for writing in. Example: If you are making a form that someone is filling out online, you can select either the Rich Text or Plain Text Content Control, and a text field will show up that allows the individual to click and write in the box that looks like this:
Another option that is given is the Check Box Content Control
which allows you to add a checkbox to your document.
Example: If there is a “circle yes or no” question on a document, use the Check Box Content Control instead to make it accessible:
Have you received all the required training?
Under the Developer tab, there is also an option to use the Date Picker Content Control which allows you to insert a date picker to your document.
Example: Perhaps you are asking someone to fill out their birthday online. Instead of having them type out the date manually, the Date Picker Content Control allows them to select the date by using a calendar provided:
...
The blue boxes in the pictures below represent form fields. Sometimes extra form fields can be accidentally added, and can look something like this:
The picture below represents what a correct form field should look like:
To get rid of extra form fields, click on the form and then click the 3 grey dots and hit Delete. This will delete the entire form field, so you must go back in the Developer tab and re-add whichever Content Control was in place.
Using Alternative text
When any image/snipping is used in a Word/PDF document, it is important to ensure that the information you are trying to convey can be interpreted by those who may not be able to see the image.
...
Right click on the image/snipping in your document.
Click on the Format Picture button.
In the right-hand menu that pops up, click on the Layout and Properties symbol.
Select Alt Text.
In the Description field, describe the image/write the alt text.
Once you are satisfied with your alt text, click the exit button to return to your document.
Note:
The alt text will automatically save once you exit out of the format picture window.
Checking accessibility
Microsoft Word has a built-in accessibility checker that allows you to review your document and ensure that it is accessible for users who have disabilities.
...
Click on the Tools tab at the top of your Adobe PDF file.
Look for the Edit PDF tool and click Open.
You can now erase any of the Content Controls you previously added in your Word Document. Click on the writing (e.g. “Click here to enter text.’”) and erase the text you wish to delete.
Once you have finished erasing all of the Content Controls, click on the Tools tab to return to all the tool options.
Click Open on the Prepare Form tool, to return to your fillable PDF. (It may ask you to save your file before opening the form).
...