Simple Online Solution for Protecting PDF Files

Improve your data security by password protecting any PDF document online.
Drag & Drop the File(s) Here

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Choose a PDF File

Protect any of your PDF documents in a few clicks. Select a PDF from your computer or cloud storage or just drag and drop a file into the box above.

Easily Encrypt a PDF online

Password-protect your PDFs and prevent them from unauthorized access. Only trusted recipients will be able to open and edit your documents.

Protect PDFs in the Cloud

Encrypt PDFs without downloading any additional software to your computer or phone. Save time and protect your documents online.

Absolutely Free

Forget about expensive software and time-consuming installations. AltoProtectPDF allows you to protect your PDFs absolutely for free.

Keep Your Data Secure

AltoProtectPDF keeps your documents private. All the files are securely uploaded and processed. Once you’ve downloaded your PDF, it is deleted from our server.

Encrypt PDFs on Any Device

Our app is compatible with all major operating systems like Windows, Mac OS and Linux. You can easily password-protect PDFs on any Internet-connected device.


File extension .pdf
Internet media type application/pdf
Description: The Portable Document Format (PDF) is a vector-based file format introduced by Adobe Systems in 1993. It was primarily designed for opening and editing documents on various desktop and mobile devices regardless of the operating system installed. PDFs can contain both text and images. Every page of a PDF file has a fixed layout and retains its structure when shared, printed, or downloaded to another device.
Technical Details: A PDF is a 7-bit ASCII file. It is based on the PostScript language and contains the description of a flat document with a fixed layout and all the embedded elements, such as graphic objects and fonts (in case the file includes text sections). PDF documents may also contain fillable fields, as well as interactive elements, i.e. hyperlinks, bookmarks, buttons, etc.
Developed by ISO
Initial Release: 15 June 1993
Useful links:


How-to guide

How to protect a PDF with a password online

  1. Open the app in your web browser.
  2. Within AltoProtect, click Choose File and browse for a file on your hard drive.
  3. Import a document from your cloud storage service (make sure pop-ups are allowed).
  4. Specify a password for your PDF. Avoid easy-to-guess sequences. Click Protect File Now!
  5. Wait while your password-protected document is being prepared for downloading (see the progress bar).
  6. Download the resulting PDF to your device or save it to your cloud storage service account.
  7. Click Work on your PDF to edit the document online (i.e. redact, sign, or share it with anybody).
  8. Click Start over again if you want to protect another PDF file.

How to Protect PDF Files

Add extra protection to the documents with sensitive data using our online solution. Password protect your docs unlimitedly from the smartphone or computer.

How to Protect PDF Files Online

Online document protection is one of the easiest ways to add an authentication layer to your document. This operation is easily completed with Alto PDF service. Available from any internet-connected device this solution works perfectly no matter you are using a tablet, smartphone or computer. It makes protection fast, simple and safe, not only through the usage of the latest security methods but thanks to the location of the platform in the cloud. It also not requires registration and all operations are made anonymously.

Samples processing with AltoPDF is easy and fast, thanks to the following step-by-step instruction:

  1. Open the web-service and add to it the document.
  2. Use drag and drop box, browse for a file or add it from the cloud.
  3. Lock document, using a complicated combination, at list eight digits long. 
  4. To see the correctness of password click at eye symbol. 
  5. Submit changes and save the file to the needed storage.

The usage of the online-based solution guarantees saving time and internal device’s memory. It is the perfect solution both for those who work with the documents rarely and regularly. In particular, it has no limitation of files per day or hour. Even working with documents regularly is time-saving. 

Having a locked document you can easily share it with any person by any communication channel, not being afraid of data loss or information fraud. 


How to Protect PDF Files With Google Chrome

Being widely known and loved by the majority of internet-user Chrome becomes not only a useful browser but also a powerful platform for additional tools. Its ability to integrate into different mobile and desktop versions and integrate all search results from different devices of any user makes this application universal. It supports several extensions, that help to personalize the design of the browser and its toolkit, according to user’s needs. Adding document protection features is also available in Chrome. One of the safest and most trustworthy services is the Alto Password PDF extension for Chrome. 

To add the protection to your PDF with Alto extension follow these steps:

  1. Go to Chrome Web Store and find an extension by name via the search engine. 
  2. Install the solution to your browser and open it by clicking at its logo.
  3. Add document using Choose a file option or add it from Google Drive.
  4. Specify the password to the document.
  5. Download file or save it in the cloud.

The service is easily installed and completes the locking process in a half of a minute. It is very simple in use having the self-explanatory interface. After you integrate this extension in your browser you get a perfect tool for unlimited protecting numerous files. It is secure, has no registration or payments and is always available from your browser. The service saves time you could spend on the search and installation of the software or selecting a secure online-baed solution.

Using Google Chrome

How to Protect PDF Files in Windows

Unlike Mac, there is no password protecting feature in Windows by default. It brings the problem that can be solved by usage online service, Google extension or the software. Most windows users process their files with MC Office Pack or Microsoft Word in particular. this solution has lock function, but it is a special one. First of all, you should know that Any PDF opened in Word automatically turns into.doc file. To get locked sample one should not just protect file but also use the Save as option. 

To protect document on Windows with Word use the following tips:

  1. Open your file in Word.
  2. Go to the File menu and choose Save as an option.
  3. Specify a folder for file storage.
  4. Select PDF as output format.
  5. Go to Options, scroll down and select encryption option.
  6. Insert password in the pop-up window and save changes.

Locking file on Windows with Word is easy if it is already installed on your desktop or laptop device. It is necessary to install MS Word or full MS Office pack to your device if you do not have it yet. Go to their official website and download the installation file from it. Next, you will need to open and install the service to your computer. 

Also, it is possible to use an online-based solution if do not have time on the installation of the software.


How to Protect PDF Files With Preview on Mac

Mac is one of the systems that has, among its basic programs much more pre-installed features than other systems. They are simplifying the life of their users, having the set of basic solutions for documents viewing, creation, editing, management, locking and unlocking. In particular, PDF files are easily opened in Preview and can be created, as well as edited with Pages. The protection option is available on Pages. The process takes a minute and encrypts the template from everyone who tries to open it.

To lock your sample with a password using Mac, follow simple instructions, given below:

  1. Choose the file you need to lock.
  2. Click at file’s options and select Set Password out of them.
  3. Enter the combination of letters, symbols, and numerals to protect PDF.
  4. Click at Set Password option.
  5. Save changes and file will be locked.

Processing docs via pre-installed solution gas numerous benefits. In particular, it saves time and funds. On the other hand, there is no necessity in the installation of specialized programs or searching for trustworthy online service. All pre-installed features pack, as well as protection, goes together with Mac OS in a full version for free. It is important to be aware of all features those solutions contain to know how many default document management tools you have on your computer. 

With Preview on Mac

How to Protect PDF Files With Adobe Acrobat Reader

Adobe Reader is widely known worldwide, as this is the company that founded PDF and for a long time it was the only solution, able to make operations with this file type. Adobe Acrobat has a multi-functional toolkit available from any device. It is the software that can is available in mobile and desktop versions. It can preview PDFs, edit their components, manage pages, save them in any needed format, except for PDF. Also, it unlocks and locks files with a password.

Adding protection to the document with Adobe Acrobat is Possible by following those instructions:

  1. Open PDF document with Acrobat.
  2. Go to tools, submit a protect option.
  3. Go to Encrypt option, click on it and choose Encrypt with a Password.
  4. Choose Require a Password option and insert the combination.
  5. Submit changes and save the encrypted file. 

Acrobat is available in trial and paid versions. Most features are available in the free version, but they are limited if there is no subscription payment after seven days. If there is no subscription, the amount of tools, available in the trial version is decreased. The registration is also obligatory. It helps to synchronize documents of every subscribed user, to be available from any device and makes Adobe Document Cloud available. It works offline but some options are synchronized after the device connects to wireless or wired internet.

With Adobe Acrobat Reader


Go to to create safe and reliable protection for your document. AltoProtectPDF is an online service that enables you to lock the file and have personal or common access. For that, select a file, create a password and save it to your computer.

Did you know?

You can send out documents to be signed

Only users who have the password can open a locked document. So it’s absolutely safe to share your docs via email. With the help of the online editing tools, you can not just format the document - but also send it for signing. Collect signatures of up to twenty people and get an email notification when the document is signed.