Electronic Document Signature Project (PDF Manipulation/Editing Experience Required)

I need to build an electronic document signature system, like HelloSign [login to view URL], that can be integrated into my website. If you do not have experience doing something like HelloSign and/or experience with PDF manipulation/editing, this is probably not a fit for you. I need a developer that is able to understand the PDF libraries and solve the complicated problems around this. This is NOT a project you can utilize "web hacking" for, you must be able to develop proprietary code for it. PDF Manipulation and Editing knowledge is key here. I do not want to license someone else's software, I want this built for my own proprietary use for my users. All features need to be mobile responsive. You are building the backend and the front end. The design does not need to be amazing, but needs to be user friendly and match my current site schemes. Specifically, I need: - PDF and Word document uploading - Combine PDFs - Standard Editable Fields and Customizable Fields that can be placed over the PDF or word that can be filled in by other users - Ability to sign documents digitally and on a device in person - Ability to send envelopes with EDS documents to user email addresses - Console for the user who initiates the PDF EDS and the receivers who receive it - Stored Templates for Users with preset fields - Saved forms that users can utilize for like the EDS that receive answers from users and are saved to the Console - Document Audits that Track all Actions of Users with Documents from the Console - User ability to see document status from Console and for users to receive email notification to sign, updates on the process, and when documents are signed (SendGrid account exists and will be used for this) - Branding on document header or footer as fields - Users able to write comments on documents and for other users to see the comments and reply to them within the system - A "Quick Send" version where a document is uploaded, no fields exist, and only the signature field is required to be filled in after it is sent - Mass send to unlimited email addresses - Ability to download documents from the Console - All users received fully signed document when all users have signed - Documents from EDS must be time stamped for when they were executed by all parties - User ability to upload, auto-create a default, or sign and save signature for themselves for quick usage Security is of the utmost importance for this project. It is fine to build this as a stand alone app within my platform and I can have my developers tie things together later. As I have had a lot of problems with developers that say they can do this and are unable to figure it out, I want to do a fixed price contract that is paid upon guaranteed delivery. Please do NOT enter a bid for this project if you do not have the skills and abilities to actually do it. Please bid the price that is acceptable to you for this project.