This is the code to have content doc ids emailed to you

EmailContentDocIdsApex.cls

// get the contentDocumentIds in the system and put them in a list to use for CDL query
// after we have our CDL Query, use the list of included objects to loop through and decide if the ContentDocumentId makes the cut for our final list of contentDocumentIds
// take the final list and make it 1 contentdocumentid per line and attach it to the running users record
// file is content-doc-ids.txt and it should be placed in the folder where you are running the script where the logs/content-doc-ids.txt file is (if the script ran already, you should see the old file there)

/**
    BELOW IS ALL THAT SHOULD NEED EDITED TO BE ABLE TO USE .... PUT API NAMES AND RUN IT AND HOPE TO GET AN EMAIL
 */
String[] objectsToInclude = new List<String>{'Account','Contact','User'};

String[] theIds = new List<String>();
String[] theFinalContentDocumentIds = new List<String>();
String[] logsTosave = new List<String>();
// get a base list of ContentDocumentIds from the system
for (ContentDocument cd : [SELECT Id FROM ContentDocument]) theIDs.add(cd.Id);

// get contentdocumentlinks and pass in the list of Ids of ContentdocumentIds that the system makes us filter on for ContentDocumentLink object queries
ContentDocumentLink[] theCDLs = [SELECT id,contentdocumentid,linkedentityid,linkedentity.type from contentdocumentlink where ContentDocumentId in :theIds];

// this is where we will loop through CDLs, and add it to the "finalListofContentDocumentIds" if our object list includes the one in the current cdl record (LinkedEntity.Type)
for (contentdocumentlink cdl : theCDLs){
    logsTosave.add('Object : ' + cdl.LinkedEntity.Type);
    logsTosave.add('Object Id : ' + cdl.LinkedEntityId);
    logsTosave.add('ContentDocumentId : ' + cdl.ContentDocumentId);
    if (objectsToInclude.contains(cdl.LinkedEntity.Type)) {
        theFinalContentDocumentIds.add(cdl.ContentDocumentId);
        system.debug ('ContentDocumentId : ' + cdl.ContentDocumentId + ' added to Final List because it is on object : ' + cdl.LinkedEntity.Type);

    }
}

// print out the final list of contentdocumentids as debugs

logsTosave.add ('Final List of ContentDocumentIds: ' + theFinalContentDocumentIds);
logsTosave.add ('Final List of ContentDocumentIds: ' + String.join(theFinalContentDocumentIds,','));
logsTosave.add ('Final Count of ContentDocumentIds: ' + theFinalContentDocumentIds.size());

// overkill notification options, should attach content-doc-ids.txt to your User record, and also email you the list.
// content-doc-ids.txt is in the "logs" folder and needs to have these ids pasted into it.

String theCDIdsListTextFileBody = '';
String theCDIdsListAttachmentFileBody = '';
for(String cdId : theFinalContentDocumentIds) theCDIdsListTextFileBody += cdId + '<br/>';
for(String cdId : theFinalContentDocumentIds) theCDIdsListAttachmentFileBody += cdId + '\n';
theCDIdsListTextFileBody += '<br/><br/><br/><br/><br/><br/><br/>';
for(String logitem : logsTosave) theCDIdsListTextFileBody += logitem + '<br/>';

ContentVersion cv = new ContentVersion();
    cv.Title = 'content_docs_ids.txt';
    cv.PathOnClient = 'content_docs_ids.txt';
    cv.VersionData = Blob.valueOf(theCDIdsListTextFileBody);
    cv.FirstPublishLocationId = UserInfo.getUserId();
insert cv;

logsTosave.add('Added content_docs_ids.txt file to user record');
logsTosave.add('Triggered email to running user');


// email us the details we need plus some debug logs
Messaging.SingleEmailMessage message = new Messaging.SingleEmailMessage();
message.setToAddresses(new list<String>{UserInfo.getUserEmail()});
message.setSubject('[Complete] -- List of ContentDocumentIds Inside');
message.setHTMLBody(theCDIdsListTextFileBody);
List<Messaging.EmailFileAttachment> attachments = new List<Messaging.EmailFileAttachment>();
Messaging.EmailFileAttachment efa = new Messaging.EmailFileAttachment();
efa.setFileName('content_docs_ids.txt');
efa.setBody(Blob.valueOf(theCDIdsListAttachmentFileBody));
efa.setContentType('text/html');
attachments.add(efa);
message.setFileAttachments(attachments);
Messaging.SingleEmailMessage[] messages = new List<Messaging.SingleEmailMessage> {message};
Messaging.SendEmailResult[] results = Messaging.sendEmail(messages);
if (results[0].success) {
    System.debug('The email was sent successfully.');
} else{
    System.debug('The email failed to send: ' + results[0].errors[0].message);
}