So you can force a download by using Content-Disposition: attachment
Content-Disposition: inline
is the default and should display in the brows
Check you file's metadata and remove Content-Disposition entry from that file. and set content type according to the file type.
Like for text file Content-Type='text/plain'
image png Content-Type='image/png'
pdf Content-Type=application/pdf
pdfxml Content-Type=application/vnd.adobe.pdfxml
If your file's Content-Type is binary/octet-stream then it will download instead of display.
Thanks