Sample Code:
Set contentDocumentIds = new Set();
List cDocLink = [Select id, ContentDocumentId from
ContentDocumentLink where LinkedEntityId = :ParentId];
for(ContentDocumentLink contentDocLinks : cDocLink) {
contentDocumentIds.add(contentDocLinks.ContentDocumentId);
}
delete cDocLink;
delete [SELECT Id FROM ContentDocument
WHERE Id in :contentDocumentIds];
List cDocLink = [Select id, ContentDocumentId from
ContentDocumentLink where LinkedEntityId = :ParentId];
for(ContentDocumentLink contentDocLinks : cDocLink) {
contentDocumentIds.add(contentDocLinks.ContentDocumentId);
}
delete cDocLink;
delete [SELECT Id FROM ContentDocument
WHERE Id in :contentDocumentIds];