Adobe acrobat - Layers issue

Each layer is indeed only one page. You will need to add a separate layer for each page of each document to achieve what you described. This process can be automated, though, using a custom-made script.

Hi there

Hope you are doing well and sorry for the trouble.

You can import layers from a PDF or image file into a target PDF. Supported image file formats are BMP, GIF, JPEG, JPEG 2000, PCX, PNG, and TIFF.

1. Click the Layers button in the navigation pane.
2. Choose Import As Layer from the options menu
3. In the Import As Layer dialog box, click Browse and locate the file to import. If the source file is a multipage document, enter the page number you want to import in Page Number. If the target file is a multipage document, specify the Target Page Number in the Preview section of the dialog box.
4. Select one of the available import options available.

For more information please checkout the help page https://helpx.adobe.com/acrobat/using/pdf-layers.html#import_layers_acrobat_pro

Hope this information will help

Regards

Amal