Unable to to edit pdf files which have been opened from Drive

Using Chromebook, ​Kami​ only work​s​ ​when​ opening pdfs from ​Gmail​, ie it does not work ​when ​opening pdfs in Drive. Therefore, ​it is necessary to ​download the file from Gmail to the Downloads folder ​in Chromebook ​and then use Kami to open the downloaded file. ​Edits are made and the file is saved to Drive.​

If a file is saved to Drive directly from Gmail and then use Kami to open the file it is not possible to edit the pdf. Or, if the file is saved to Drive directly from Gmail and then​ download to Downloads and Kami is then used to open the file it is not possible to edit the pdf​​.​ ​Please advise​.