You could blindly use Joomdonation migration tool and ypu wil discover a total mess !
Why, because of the different directory structures that are not migrated with that tool. What are they ?
Docman allows you to assign any file storage directory to any category or sub-category. You can decide that file-s for Category A are stored in directory A and files for sub-category A-1 are also in directory A. EDocman does not !
For EDocman, you can decide or hierarchical directory structure of not. If not directory structure all file shall be in root directory (whatever it is). If you decide for hierarchical directory structure, then you have limite choice that may be in total contradiction with the file structure of Docman.
Let see why : Category A files will go in directory A. If I tell EDocman to store files of sub-category A1 = directory A, it creates a sub-directory A in directory A. If I keep empty the directory associated with Sub-category A1....it does not go to directory A, but to root ! Therefore you are trapped unless to create a sub-directory for each sub-category within Docman before migration and do not use the file "move" tol to create a structure compatible with EDocman.
Once you do it, migration is rather reasonable except :
1) Description associates with Categories are not kept. It's messed totally. I have found descriptions from any category reported in a category.
2) The same for files, description are messed as for categories
3) ACL are not kept for categories, you have to go manually modifying the ACL of each category.
4) ACL are not kept for documents, you have to go manually modifying the ACL of each document.
As a summary, just do it if :
1) you cannot afford to pay for Docman that much expensive than Edocman, otherwise keep it Docman. Migration tool fro EDocman will cost you hours of modifications and headaches
2) You have a limited number of documents to correct the result.
Drastically missing within EDocman :
1) A feature to move files from directory keeping of course the links with the document
2) A feature to select a file from the server. When the file is already there, you shall reload it and the system is rather poor for large files !
3) A feature to assign specifically a directory to a category regardless of it parent one.
Remembre as well that even if you succeed to migrate you will have to change all the "links" in article or any other content and that's can only ne done manually.