Script transfer guides to artboard

Press Shift+O to activate the Artboard Tool then create a guide by dragging on the rulers as usual. If you drop the guide into the active Artboard the guide will stay within the artboard bounds. 

Hi @Nicky G., this is a cool idea. I get annoyed guides messing up my pasteboard, too. It wasn't as straightforward to write the script as you might think, but I think I've got it working. Let me know how it works for you.

- Mark

/**
 * Change all "pasteboard" guides to "artboard" guides
 * when they intersect with one or more artboards.
 * @author m1b
 * @discussion https://community.adobe.com/t5/illustrator-discussions/script-transfer-guides-to-artboard/m-p/13749896
 */
(function () {

    var doc = app.activeDocument,
        artboards = doc.artboards,
        items = doc.pathItems,
        counter = 0;

    for (var i = items.length - 1; i >= 0; i--) {

        var item = items[i];

        if (
            item.guides !== true
            || item.locked == true
            || item.width * item.height > 0
            || !item.hasOwnProperty('pathPoints')
            || item.pathPoints.length !== 2
        )
            continue;

        var b = item.geometricBounds,
            orientation = 0,
            max = -Infinity,
            min = Infinity;

        for (var j = artboards.length - 1; j >= 0; j--) {

            var a = artboards[j].artboardRect;

            if (boundsDoIntersect(a, b)) {

                if (item.height == 0) {
                    // horizontal guide
                    orientation = 1;
                    max = Math.max(max, a[2]);
                    min = Math.min(min, a[0]);
                }
                else {
                    // vertical guide
                    orientation = 2;
                    max = Math.max(max, -a[3]);
                    min = Math.min(min, -a[1]);
                }

            }

        }

        if (
            orientation !== 0
            && !hasCommonDimension([min, -min, max, -max], b)
        ) {
            if (orientation === 1) {
                // horizontal
                setCornerPathPoint(item.pathPoints[0], [max, b[1]]);
                setCornerPathPoint(item.pathPoints[1], [min, b[1]]);
            }
            else if (orientation === 2) {
                // vertical
                setCornerPathPoint(item.pathPoints[0], [b[0], -max]);
                setCornerPathPoint(item.pathPoints[1], [b[0], -min]);
            }
            counter++;
        }

    };

    alert('Converted ' + counter + ' guides.');

})();


/**
 * Sets a path point's position
 * and converts to corner point.
 * @param {PathPoint} pathPoint - an Illustrator PathPoint.
 * @param {Array<Number>} p - [x, y].
 */
function setCornerPathPoint(pathPoint, p) {
    pathPoint.anchor = p;
    pathPoint.leftDirection = p;
    pathPoint.rightDirection = p;
}


/**
 * Returns true when bounds intersect.
 * @param {Array<Number>} a - bounds [l,t,r,b].
 * @param {Array<Number>} b - bounds [l,t,r,b].
 * @returns {boolean}
 */
function boundsDoIntersect(a, b) {
    return !(
        b[0] > a[2]
        || b[2] < a[0]
        || b[1] < a[3]
        || b[3] > a[1]
    );
}

/**
 * Returns true when bounds `a` and `b`
 * share a common dimension, for example if
 * both have the same left and right edges.
 * @param {Array<Number>} a - bounds [l,t,r,b].
 * @param {Array<Number>} b - bounds [l,t,r,b].
 * @param {Number} [tolerance] - how close in points.
 * @returns {Boolean}
 */
function hasCommonDimension(a, b, tolerance) {

    tolerance = tolerance == undefined ? 0.01 : tolerance;

    return (
        (
            Math.abs(a[1] - b[1]) < tolerance
            && Math.abs(a[3] - b[3]) < tolerance
        )
        || (
            Math.abs(a[0] - b[0]) < tolerance
            && Math.abs(a[2] - b[2]) < tolerance
        )
    )

};

Edit 2023-04-26: fixed three problems—handles overlapping artboards, doesn't create unwanted duplicate guides, and doesn't try to operate on guides that have already been trimmed by a previous running of the script. A difference is that if there are multiple artboards in line with the guide, it will span them all.