SharePoint is not designed to attach documents, still you can attach documents but it leads to poor business practice. You should understand the concept of list and a library in SharePoint.
01. SharePoint Document Library
It helps you to store and organize your documents or files. You can store the documents by uploading them to the document library and you can organize them via folders or metadata.
02. SharePoint List
It is used to store non-document information such as tasks, events, properties, clients, projects etc.
• Document Management features
There is a lack of Document Management features in a document library such as versioning, check in and check out, co-authoring, ability to open and edit documents in the browser etc. You should know that SharePoint list is not a document library by itself.
• Version History on the attached files
Lack of version history feature on the items in the list itself, is not carried over to the attached files. For instance, if you have two attachments,
and trying to make changes to one attachment and deleting the other,
if you want to restore back the deleted one, you have to check your recycle bin and restore the deleted file.
• Impossible to organize attachments or apply document specific metadata
The attachments, attached to an item will get stored at the same place and it is impossible to organize them in a folders or apply file-specific metadata the way you do in document library.
• Impossible to upload multiple attachments at once
Attaching attachments depends on classical SharePoint list or modern one. If you are using classical SharePoint custom lists with classical web parts like calendar, tasks, issues, announcements etc. you can attach one file at a time. If you are using modern SharePoint lists, you can upload multiple attachments at once.
• Turn off attachments in a list
To stop people uploading attachments to SharePoint list, you can disable attachments. To disable the attachment in the list follow below steps:
1. Find List Settings > Advanced Settings
2. Move to the middle of the page to Attachments section and select Disabled radio button
3. Click OK
• Don’t use SharePoint lists for storing documents
It is always good not to use SharePoint lists for storing documents and working documents. But it also has some advantages. For instance if you have created a Help Desk System in SharePoint it is possible. You can use SharePoint document libraries for storing documents.
• Store both the list information and documents.
Use Document Sets!
In case you have one-to-many sort of relationship, where, say, you have a client list and some documents that need to be associated with a client. Document Set functionality allows you to create folder level metadata (your SharePoint list metadata essentially) and attach files to each document set (i.e., Client). In a way, you end up with a folder (document set) for each client or project and then corresponding documents inside of each folder. On top of that, all files stored within a document set inherit metadata from the folder! So, it is almost like having a SharePoint List with attachments, except, done properly!
List of folders (document sets) with metadata (in place of a SharePoint List metadata)
Contents of a Document Set. Files are organized using metadata and benefit from all the available document management capabilities