# Placed PDF layer visibility

Object Layer Options distinguishes a PDF's own default configuration from an explicit visibility choice, including showing every layer. Use File Defaults resets that choice. Only placed PDFs in a mixed selection are changed.

The engine command `object.layerOptions` accepts `hidden` names and optional `useDefaults`. Existing calls with `hidden: []` retain their reset behavior; pass `useDefaults: false` to explicitly show all layers. `useDefaults: true` resets defaults and cannot be combined with hidden names. Every explicit choice, including all-on (`useDefaults: false` with an empty `hidden` list), is checked with one actual visibility rewrite per distinct source before any target is edited or an undo step is recorded: a PDF can list readable layers yet refuse the rewrite (for example an over-budget cross-reference history), and PDFs without readable optional-content layers cannot be rewritten at all. Resetting to file defaults needs no rewrite and is always allowed. A stored choice whose source can no longer be rewritten still fails closed: the canvas does not draw the unmodified source and PDF export reports an error. With no explicit ID, a query selects the first placed PDF anywhere in the selection; an explicit non-PDF ID remains an error. Queries include `overridden` separately from each layer's `visible` and `default` states.

Native saves use format 4 only for an explicit all-on override, on document or parent spreads, in groups or anchored: older readers would otherwise silently render file defaults. Format 4 is one reader capability shared with retained placed-graphic layer options (#1647, see [graphic-layer-options.md](graphic-layer-options.md)), so a version 4 reader understands both. Existing nonempty hidden lists retain their older semantics and format requirements. Raster and PDF export honor the choice; PDF export keeps its existing warned rasterization behavior. Embedded IDML export stores a separate PDF variant per placement and leaves original linked bytes untouched. Every placement counts there: parent-page and anchored ones too, so a page that inherits the placement does not quietly fall back to the file's defaults. External-only IDML export rejects active PDF layer choices because the original external file would lose the choice. A package's IDML copy links the placed files, so it cannot carry a choice either; the package report says so, and the packaged DesignCraft document keeps it.

This fixes visibility-state handling, not full InDesign layer/print parity. It does not implement editing the contents of placed PDFs or native INDD placement. Catalog/reference safety fixes landed in #1670.