Responsive Multi-user CMS - Based on the uploading and downloading of PDFs

I require the CMS side of a website to be created. The front-end (HTML & CSS) has already been built and is ready to be integrated into a CMS of your choice. The website needs to allow users or guests to upload PDF files and a short paragraph of text into specific categories. These articles are then viewable on the website from which guests and users can download the PDFs uploaded by the author. The header is relatively simple, a logo, a navigation bar consisting of a home link, categories link (which then drops down to show the categories), a gallery link, and contact. As-well as that there is a search bar and meta for login, signup etc The homepage consists of a slider with images and text managed by the admin (me), 2 sections for recent articles in a specific category(s), these recent article sections show the category image the article is tied to, the category name and the short paragraph of text the user entered when they created the article, a tabbed section for displaying most viewed articles, top authors, and most popular categories, there is then a section for sponsors / advertisements aswell as social media. Please see draft design posted along with this brief. The footer again is a relatively simple multi-column layout, 1 column with the same links as-in the navigation bar in the header, another with a list of categories (links) and then random about us information. There needs to be a categories page which displays all the categories and the category image. The actual article page will just display the article title, small paragraph of text along with a PDF viewer to display the PDF that was uploaded. Breadcrumb navigation may also be necessary. The gallery page, will just be a simple gallery controlled by me the admin. So this project can be made using Wordpress, Drupal, or even custom coded in PHP. If it is custom coded (and even if using a CMS) all code must be secure and bug free. Please only bid on this project if you have access to skype and don't mind chatting. Email and Skype is the preferred contact method. A github repo will be used to manage the project, so please state if you have git knowledge or not.