I’ve opened a password protected file and when I save a new copy, the password is still included. This is a feature in Preview, and Acrobat has a feature that allows removing the encryption. How do I do this with Sumatra?

Sumatra doesn’t have such functionality.

The easiest / official / reliable /secure way to remove the open with password is with Adobe Acrobat.

The problem arises when you forget your own password, then the acrobat support says you must NEVER forget it as the code is designed to not be broken.

You may be fooled into thinking my 2 bit password can be cracked I just forgot which 2 keys I accidentally pressed, Good for you IF it was just 2 keys its simple to flash through the permutations even if it was re-encoded as 5 byte characters. (40bit)

So for VERY old 40 bit encryption files or shorter 4/5 character passwords or even an “imperialistically” chosen long dictionary word just use an online service but if they ask you to handover the password first then wonder WHY! Is that not the reason you went there?

Many viewers such as Edge allow you to open a file with a password and may then allow you to print or save as new PDF.

However using “save as” in SumatraPDF will usually retain the need for the same password and will often require the same one of two passwords to save changes such as if you added comments. Print as PDF would result in an unlocked image based pdf, exactly the same as taking screen grabs.

That is, SumatraPDF will allow to temporarily ignore restrictions needed for annotation but respect DRM.

Both GuaPDF and John the Ripper can remove the password on the PDF, and are generally popular with users who forget the password and cannot open the PDF.

SumatraPDF for annotations can ignore instantly the restrictions password just the same as GuaPDF or any other DRM free PDF viewer such as Evince Okular etc. That then allows you to copy and print.

Files that are protected for opening are different, only those with OLD 40 bits can be opened within 2 days by GuaPDF and cant work with acrobat plugin DRMs

GuaPDF can be also used for
remove PDF open password (a.k.a. user password). Decryption of the file with password for opening is guaranteed for old PDF documents with 40-bit key only. This process takes 1-2 days on one modern desktop computer and could be accelerated on GPU.
Only standard PDF security is supported, neither third-party plug-ins nor DRM.

and recent comment from an experienced user of “John” which was built for Unix

Simens
John the Ripper used to work well on my Windows 7 PC but it failed recently on Windows 10 with October update. It runs two days and still not finding the password.

In the cases where acrobat is not using plugins then SumatraPDF can store your passwords for you, so the file even if using 256bits encryption is opened instantly without you remembering the password entry. So if you are prone to forgetting passwords it is a boon.

In all cases SumatraPDF is NOT removing passwords just simply ignoring the need to provide them. Resaving the file saves the need for both of those 2 types of passwords.

Okay, learn what this tutorial says.

passgeeker ###/remove-password-from-pdf
WARNING DO NOT DOWNLOAD FROM ABOVE SITE as it reportedly can download MALWARE (16/66 virus total detections)
[It will explain as above, the two types of restriction (One of which SumatraPDF will ignore when it needs to modify contents, for the other is …)]

IF you replace with safer links they will lead you to the windows FOSS alitrack/PDFCrack: A Password Recovery Tool for PDF-files (github.com)

Free software can also be tried if you want to do this.

[Link is removed as “the website is monetizing from Google Adsense”]

Before using it, you need to understand its working steps.

[Moderator note] Many dubious online sites are available and their limitations are as mentioned above. A few will admit they may not crack the OPEN password.
Without linking to any specific one you can google

“This only works for PDFs that you can open and read without any 3rd party plugins. PDFs that require a password to be viewed cannot be unlocked by this service. This is because this is not cracking.”

The correct official line if you “forget the password” is Solved: Forgot the password of PDF file - Adobe Support Community - 9277779
Unless you keep passwords to just a few characters long or always use the same few common words then you need to use brute force attack of passwords.

Remember the password or re-create the file.

I tried using a well known sample file on freemypdf where the user password is, guess for it, “user” the result was

We’re sorry!

The unlocking of tiger.pdf failed because of the following reason(s):

• Input PDF cannot be handled - Maybe it requires a password or a plugin to be viewed?
  You can fix these problems and [try again], but remember, this only works for PDFs that you can open and read without any 3rd party plugins. PDFs that require a password to be viewed cannot be unlocked by this service - If this is the case, try PDFCrack, it’s free.

So I tried the file using PDFCrack (which requires me to give -u user so that it can attempt to find the -o owner password) needless to say after about an hour it had not found that, so I aborted the run. Progress Log is not easy to interpret, but my guess is it may have eventually succeeded in that VERY simplistic case of 4-5 Latin characters (no specials) after about 4-5 hours.

Without providing owner password (just the user one) within SumatraPDF I can instantly copy or print the file contents, which is requested to be denied by the owners password. So NO need to “remove” that password.

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Out of interest I tried several online “cracker” sites with this WELL KNOWN standard file
#1 on google said File is corrupt
#2 on google said Failed to decrypt PDF file.
#3 on google said Tick the privacy box but there is none so cant upload !!
#4 wanted to download some software
#5 on google said it could open it in 1.2 million years time (unless I told it the 1st password to open file then it would instantly remove the need for the harder one which it did by reprinting the file with its own producer moniker) !!! but that’s what SumatraPDF can do too when you recreate using print.

In fairness ONE site did break the two simple passwords including “user” but I am having to wait 2 hours before I can test a more complex one !

While waiting I don’t need to enter that password to view or print, as I asked SumatraPDF to remember it for me.

OK I uploaded the same file with a longer 20 Latin character password (no complex characters) and this time it responded just as quickly, however, I got back a blank page so have to presume for now the first “success” was due to a known word.
reduced the password to 9 characters again result was also blank so tried another one but also got message
We were not able to remove protection automatically.

If you want to test a real sample protected.pdf file for yourself
I will tell you the password has 8 sequential lower case alphabetic letters plus one other character (just to add a bit of spice).
Let me know what the included 3 little words say? and how long your attempt took.

I don’t know much about Acrobat,but about how to remove or unlock password from a PDF file,there are some ways/tools for you choose,such as the GuaPDF,John the Ripper,and you will be allowed to unlock password for PDF via online (By using FreeMyPDF).

@Oneth
If you read my answers you will see SumatraPDF will “unlock” as required the pdf just the same as any other tools. There are many claims to do more by uploading your files to a 3rd party so they can save the unlocked contents for you .

Why would you give someone online permission to use your pin number?

Download my typical “locked” PDF and tell me which of your suggestions is able to unlock it. GuaPDF can only instantly open very old 40bit files (for my sample they redirect you to a commercial multi-thread product that takes days to unlock such a secured file).
"A string of nine letters or numbers takes milliseconds to crack. Add a symbol character e.g. &*%$, and your password may become cryptic enough to thwart password crackers for nearly four decades. "

Office PC: 99 years Gaming PC: 17 years LostMyPass: 120 days

SumatraPDF will open it instantly IF I add the password to the password dictionary. Also when viewed in latest pre-release I can instantly copy to paste or print without any second password.

I have done it, but I am not using Ophcrack, I am using this tool.

MALWARE LINK REMOVED

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As far as i know PDFCrack is also doing well.

Thanks for trying but please tell me what you found in my file
Your link to 4 methods shows that for my file
the first two will never work, same as most others
the 3rd wishes to install a Trojan
and I agree Windows PDF crack from

SHOULD eventually work, but was optimised for linux, thus on this slow machine, not in my remaining lifetime.

Let me know how many hours/days it takes on yours.

Thanks it was also helpful for me.

“Many online PDF password breaker service will only help you break OWNER password.”

Which is not needed to view PDF files in SumatraPDF.

The USER password to OPEN a protected file is a different beast

smallpdf .com unlock-pdf, Honestly admits
“you can only unlock the file by providing the correct password.”
freemypdf .com, Also says
“The unlocking of protected.pdf failed because of the following reason(s): Input PDF cannot be handled - Maybe it requires a password or a plugin to be viewed?”
sodapdf .com unlock-pdf,
“A password is required to open the uploaded file!”
Most Others,
“Specify the password to be used for unlocking the document(s):”

In this case SumatraPDF settings can store the encrypted password to instantly open the file.
Exactly the same as those online services but secured on your own machine.

Beware any trojan site that says download their “Guaranteed PDF password breaker” at best they are just a front end to download other demonstration tools that prove they can open files with insecure 2-5 character passwords, which as stated only takes seconds, once you try 6 its more like hours but they wont show you that.

There is no doubt that John Ripper can crack PDF passwords, but I am pursuing the simplest method. After all, there are not many users who are proficient in John Ripper. It involves too many text operations. I personally would not give priority to it. It, in comparison, online software (pdfunlock and freemypdf ) does better than John Ripper, only from my personal advice.

tried multiple sites with that name using my sample that opens instantly in SumatraPDF where I can print it even though that’s set to be protected too

pdfunlock.online = Error: Unable to process file
pdfunlock.com leads to soda which says " A password is required to open the uploaded file.if you know the password, enter it below to unlock the file. Clearly if I give it either one of the two passwords it opens and rewrites that file without needing either password for next time. (But so what I can do that in SumatraPDF, without it changing the file)

I tried a few others that are not listed above with as expected results
site 1) This is an encrypted file
This file is encrypted by the open password, we can’t get access to the content. Please enter the correct open password, and try to convert it again.
site 2) Error: ENCRYPTED.pdf: The PDF file is encrypted and needs a password.
Do you know the password?

thank you a lot, such needed info for me rn

The free version of Adobe Reader can only view PDF but not remove the password. You can upgrade to the latest version to do what you want, but this is not free.
I saw someone recommend the John Ripper. Yes, this tool can be used to removed PDF passwords, but for ordinary users, it is not that simple task. It has been running on my computer for 40 minutes and did not satisfy me.
Some online methods are worth trying.

SumatraPDF is “free” but consider donating, better than Adobe Reader it can work with password protected files, but just like Reader will not change the opening password. MuPDF is used to control the PDF opening and like full Adobe Acrobat can change the passwords and save a PDF without them. MuPDF is AGPL Open Source.

Password crackers can take between milliseconds and Centuries depending on levels of password complexity see my simple challenge file which my SumatraPDF opens in one second but no one has opened yet using an online cracker.

An online cracker can only open the simplest of passwords in minutes otherwise they will ask you to give them the password ! ! ! ! send me your file with $100 and no promises but I may eventually send it back unlocked.

I just tested several software on the computer to delete the PDF password.
I have a PDF with a password of 111111, it was easy to remove the PDF password by GuaPDF.
https://www.guapdf.com/
This may be the reason why the password is too simple because after I uploaded another PDF file protected by a complex password to GuaPDF, I got the result of failure (I need to pay for the premium version to work ). I guess this type of free software can crack or remove simple passwords, but it’s useless for complex passwords.
Next. I tried professional third-party software on my mother’s computer. Compared with other software, it didn’t ask me to key the password before removing it.
[duplicate link to multiple review site including Acrobat and GuaPDF mentioned above removed]
This is worth cheering. I suggest users who want to remove the password from the PDF without knowing the password.