What kind of file is doing this? I generally have no problems downloading files using Chrome, but there are certain files that I've noticed only download as a 1 or 2 KB file.
Where are the files being downloaded from and what OS? Anytime Windows is part of the mix I always use Google Drive in the cloud as a transfer point or just let the .pdf say in Drive in the cloud. Last week Google Drive added Microsoft Documents that downloaded to my Nexus 5 in a new App folder called Documents.