ASCM is a common mistype for ACSM which is something you were probably looking for - Adobe content files. There is no ascm to pdf conversion possible, BUT acsm to pdf conversion is somewhat possible. Some e-books sold on internet can be delivered as .acms files which are meant for Adobe digital platform. They actually cannot be "converted" to any other ebook format, because they do not contain it, but you can still get your PDFs. Basically, .ascm files are just authorized links (purchase tickets) so the user can download and view his legally purchased books.
The only way to actually "convert" acsm to pdf would be to install Adobe Digital Publications and authorize your computer Adobe ID. Then open your .ascm file and load it Digital Editions. After the book is downloaded, you can find it either in PDF or ePUB form saved in the default Adobe Edition ebook location in your user account and documents folder.
Sometimes you also need to remove the DRM protection from the resulting .pdf document, because these files are still protected by Adobe DRM which sometimes cannot be read on OS X or Kindle platform.Open ASCM file Open PDF file