Increase Max Attachments
You can increase Number of attachments which can be added to particular documents via Customize Form.
Let's assume we need to increase Max Attachment limit for Quotation to five. Following will be the steps to achieve this.
Step 1: Go to Setup > Customize > Customize Form.
Step 2: Enter Form Type.
In our case, it will be "Quotation".
Step 3: Increase Numbers under the Max Attachments field.
After increasing numbers update the Customization Form.
Note: Max limit/size of an attachment is 1MB.