Namely, is there any support for marking up existing PDFs, and will this work if your form is behind a login?
Currently, forms need to be created using our WYSIWYG design tool - this creates the layout of the web-form and the resulting PDF. There is no way at the moment to import an existing PDF form to mark up - though I am working on a solution to this. (To get around this, some users have used a screenshot of their static PDF form, and then placed the text fields and checkboxes over this image - it works, is quick, and they don't have to pay someone to make them a fillable PDF - though, this is less than ideal if you already have a dynamic acro-form)
Our forms will work from behind a login. It uses iframes to embed the form, so as long as the user has access to the 'net, they will see, and be able to use the form. We also have an authorisation script that you can put on your site to protect the iframe embed code so that people can't copy the HTML and put your form on their own site.
Please feel free to contact me if you have any other questions - my email is in my profile.