Create and modify a file extension

for your custom files - 

Have a look at this page: https://docs.appian.com/suite/help/19.2/Text_Doc_From_Template_Smart_Service.html

You can store text doc templates with any extension you wish.

So you can have CTO_template.cto having one or more keys* to support your metadata.

Then when you upload your PDF, you can then create a new .cto file, name it whatever you like, and load it with metadata.

* In the past, I have had use cases in which I found it appropriate to use 1 simple key, e.g. ###docBody### to load the entire document. If you have detailed insight into the standard formatting of these data files, it's ideal to design the template as close to complete as possible.  e.g.

field1: ###field1###
field2: ###field2###

and not

###docBody###

for your custom files - 

Have a look at this page: https://docs.appian.com/suite/help/19.2/Text_Doc_From_Template_Smart_Service.html

You can store text doc templates with any extension you wish.

So you can have CTO_template.cto having one or more keys* to support your metadata.

Then when you upload your PDF, you can then create a new .cto file, name it whatever you like, and load it with metadata.

* In the past, I have had use cases in which I found it appropriate to use 1 simple key, e.g. ###docBody### to load the entire document. If you have detailed insight into the standard formatting of these data files, it's ideal to design the template as close to complete as possible.  e.g.

field1: ###field1###
field2: ###field2###

and not

###docBody###

Perfect. That helped.

Thanks Robert.