> For the complete documentation index, see [llms.txt](https://helpdesk.ldtsoft.work/ldt-digital-downloads/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://helpdesk.ldtsoft.work/ldt-digital-downloads/sell-your-digital-products/how-to-protect-pdfs-and-ebooks.md).

# How to protect PDF files and e-books

Watermark every PDF or EPUB with the buyer's details, add a PDF password and decide what readers may do.

Protect the PDF and EPUB files you sell: stamp each buyer's copy, add a password and limit printing or copying in LDT Digital Downloads.

### 1. Open the e-book security settings

Go to **LDT Digital Downloads → Settings → E-book security**.

![Shopify admin sidebar with Settings in the LDT Digital Downloads group, and the E-book security row in the app settings list](https://1863660695-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F6iG7j4lDhziM0FqdCCU8%2Fuploads%2Fgit-blob-10d406dcf894b9723d744d618551baeb63b4605c%2Fsettings-nav-ebook-security.png?alt=media)

The page is in three parts: two viewer sections (**PDF viewer** and **Other e-books viewer**), a **Watermark settings** card with a **PDF watermark** and an **EPUB watermark** block, and a **Password settings** card for PDF files.

### 2. Stamp every PDF with the buyer's details

In **Watermark settings → PDF watermark** turn on **Auto stamp**.

![E-book security settings with the PDF watermark card and Auto stamp switched on](https://1863660695-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F6iG7j4lDhziM0FqdCCU8%2Fuploads%2Ff8uY94mEgV7BdmAZpVOz%2Fsettings-ebook-watermark.png?alt=media) From then on the app writes a watermark onto the PDF it serves, so the copy a customer downloads carries their own order details.

* Choose which pages carry the stamp: **First page only**, **All pages**, **Even pages only** or **Enter page range**.
* Click **Customize PDF watermark** to write the text. The editor lists the variables you can drop in: **Order name**, **Order date**, **Order contact email**, **Customer firstname**, **Customer lastname**, **Shop name**, **Item name**, **Item SKU**, **Item quantity** and the **Billing address** fields.

### 3. Stamp every EPUB the same way

In the same card open **EPUB watermark**, turn on **Auto stamp EPUB** and click **Customize EPUB watermark** to write the text. The same variables are available.

### 4. Add a password to the PDF

In **Password settings**:

* **Document open** — set the password a customer has to type before the file opens, and the owner password that keeps control of the document.
* **Document permissions → Allowed actions** — tick what a reader is allowed to do with the file, such as printing or copying text.

Password protection applies to PDF files.

![E-book security settings with the Password settings card](https://1863660695-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F6iG7j4lDhziM0FqdCCU8%2Fuploads%2FHHrSRIWWrTcae2USmImG%2Fsettings-ebook-password.png?alt=media)

### 5. Decide how the file reads online

The **PDF viewer** and **Other e-books viewer** sections control the online reader rather than the file itself:

* **PDF content online access** and **E-books content online access** — whether customers can read in the browser at all.
* **E-book viewer** / **Online reader** — the reader style, including **PDF viewer: Continuous** and **PDF viewer: Single Page**.
* **Default reading settings** — **Font size**, **Hyphenation** and **Background theme**.
* **Hide download button** — hide the download button so the file can only be read online.

### Result

Every order gets a copy stamped with that buyer's details, the PDF can ask for a password, and the online reader follows the settings you picked.

### Troubleshooting

* **The file is not stamped.** PDF files and EPUB files must be smaller than **100 MB** to be stamped; a PDF larger than that cannot be password protected either. Compress or split the file first.
* **The watermark or password options are not editable.** These settings need a plan that includes e-book stamping or PDF passwords — check your plan under **Settings → Pricing**.
* **Customers cannot open the file.** A password protected PDF asks for the password from **Document open**; tell the buyer what it is, or turn the password off and keep the watermark.

### Related

* How to create and sell a digital product
* How to deliver video and audio