If you uploaded a file to use in a Lead Capture Form or Resource Library then you can replace that file without having to change the Form / Library.
To do this, visit the Uploads Dashboard and click the 'Settings' button for the relevant upload:
Next, scroll down to the 'Replace File' section:
If this file is being used in any existing Lead Capture Forms or Resource Libraries they will be listed here.
Please be aware that if you choose to replace this file with a different version then every Lead Capture Form and Resource Library that uses this file will be automatically updated.
Finally, click the green button to upload a new version of this file: