All Spots To Process as part of saved PDF export preset

Thanks all for the feedback. I was just looking at the request as part of the export pre-set, not running a script, converting in Acrobat or using the checkbox in the Ink Manager settting. I've added a feature request, for what it's worth. 

If you export to PDF Interactive then you won't have to do any conversion, spots are automatically changed - in my tests anyway.

File>Export>PDF Interactive from the drop down. 

It's a menu proof setting by your name in the setings - so this would make it all RGB. 

Does that help?

A script can do it for your proofs so you don't have to remember toggle to interactive pdf each time. 

// InDesign JavaScript (ExtendScript)
if (app.documents.length !== 0) {
    var doc = app.activeDocument;

    // Prepare default file name: DocumentName_proof.pdf
    var baseName = doc.name.replace(/\.indd$/i, "");
    var defaultName = baseName + "_proof.pdf";

    // Prompt for save location with default name
    var pdfFile = File.saveDialog("Save Interactive PDF", defaultName);

    if (pdfFile !== null) {
        // Clean up document metadata to avoid "Proof" titles
        doc.metadataPreferences.documentTitle = baseName;
        doc.metadataPreferences.author = "";
        doc.metadataPreferences.description = "";

        // Set export options
        var pdfExportPreset = app.interactivePDFExportPreferences;
        pdfExportPreset.pageRange = PageRange.ALL_PAGES;
        pdfExportPreset.exportReaderSpreads = false;

        // Ensure file has .pdf extension
        if (!/\.pdf$/i.test(pdfFile.name)) {
            pdfFile = new File(pdfFile.fsName + ".pdf");
        }

        // Export to interactive PDF
        doc.exportFile(ExportFormat.INTERACTIVE_PDF, pdfFile, false);
        alert("Exported to Interactive PDF:\n" + pdfFile.fsName);
    }
} else {
    alert("No document open. Please open an InDesign document first.");
}

I personally just do the switch in the Ink Manager in InDesign before export. You can always toggle back to spots (as a whole or selectively) if you need them spot for another purpose.

Or done in Acrobat? 

Can't be done in the UI (as far as I know).

Can probably be done with a script that's invoked "on export".