Script to flip objects on all pages

Hi @jacobs40370360, I'm sure there are further complexities, but here is a simple approach that does what you ask. See if it helps.

- Mark

/**
 * Flip Items Horizontally.js
 *
 * Flips every page item horizontally, unless its layer is locked or not visible.
 *
 * @author m1b
 * @discussion https://community.adobe.com/t5/indesign-discussions/script-to-flip-objects-on-all-pages/m-p/15084291
 */
function main() {

    var doc = app.activeDocument,
        items = doc.pageItems;

    for (var i = 0; i < items.length; i++) {

        var item = items[i];

        if (
            undefined == item
            || !item.hasOwnProperty('geometricBounds')
            || !item.itemLayer
            || item.itemLayer.locked
            || !item.itemLayer.visible
        )
            continue;

        item.transform(
            CoordinateSpaces.PARENT_COORDINATES,
            [[0, 0], BoundingBoxLimits.GEOMETRIC_PATH_BOUNDS, CoordinateSpaces.INNER_COORDINATES],
            app.transformationMatrices.add({
                horizontalTranslation: item.geometricBounds[3] - item.geometricBounds[1],
                horizontalScaleFactor: -1,
                verticalScaleFactor: 1,
            })
        );

    }

}
app.doScript(main, ScriptLanguage.JAVASCRIPT, undefined, UndoModes.ENTIRE_SCRIPT, 'Flip Items');