The way the Media Libary works is that files are cached on our servers for a while after deletion in the Media Library, so subsequent uploads with the same file name get a sequential number appended to the end. Files are never overwritten.
The upload year and month also form part of the path to the document. For example, this URL indicates that the file was uploaded in February 2013:
http://mdcaptives.files.wordpress.com/2013/02/fa-execsummary3.pdf
Here are suggestions:
1) Instead of giving out direct links to a PDF, create a page with a link to the download, and point people there. That way, you can modify the link to the file whenever you revise it and upload a new version, and folks will always be downloading the latest one.
2) Let us know the URLs of the files you would like us to permanently delete from the server. This method is best for occasional needs only.
Also, mdcaptives was the domain name used when this blog was started. It is no longer valid with benefitsfordocs being the operative name for this site. Is there any way to modify this?
If you want to change the "mdcaptives" part of your address to something else, you can follow the instructions for changing a blog address
Let us know if you need anything else.