With 'single file', do you mean a single project?
If you mean a single project, the short answer is no: You need to use source control if you want to be able to work in the same project with multiple people simultaneously.
Of course, you can also both get a local copy and copy paste any changed files to a central location, such as a network drive. This process is however very error prone (forgetting to put files files, forgetting to get files, overwriting each other's work, etc.)
You can share a single project via a network drive and work with multiple authors. You just won't be able to work in the same project simultaneously without some form of source control.
If by single file you mean a single HTML file, then the answer is a definite no. And even when you use source control, doing something like that would mean merging on HTML code level. Not something I would recommend to anyone.
Meanwhile, from the "well duh" category, if you just want more than one person to work on a project but not simultaneously, just install RoboHelp on one PC and each take turns using that PC.
By a single file, I mean a single project but we don't want to work simultaneously. We have Robohelp installed in our systems and we want to work on our own systems in a single project. Installing a server would be quite expensive so was looking for an alternate option.
Even I have the same problem. We have tree people working on the same project file in Robohelp 10. The copy paste option is really an overhead and is very error prone.
Please suggest any other option without purchasing robohelp server.