If a secure PDF doesn’t work for your needs, you can export to PDF from InDesign and then create a Fixup in Acrobat that can convert pages to images. You can save the Fixup for future use.
To Create a Fixup in Acrobat
1. Choose Print Production from the Tools menu and choose the Preflight tool to open its dialog.
2. Click on Options in the upper right of the dialog and choose Create Fixup… .
3. Enter the fixup name in the Name field.
4. From “Fixup category”, choose Pages, and then click on “Convert page content into image” from “Type of fixup”.
5. Choose the desired image resolution, keeping in mind that a high resolution for a multipage document can create a rather large file. You may want to test the resolution that works best for your needs.
6. Click OK. If you have a document open, it will apply to the current file.
7. The new fixup will appear in the Preflight dialog under the Pages and can be run on any open PDF by selecting it and clicking on the Fix button in the lower right of the dialog.