Why am I getting an error message when trying to combine files into one PDF file?

[LBExj]

When I select multiple PDF files and try to combine them into one document, I get a message that "Adobe Acrobat has encountered and unidentified error" and no file is being created. This problem has only recently started as I have been able to merged documents in the past.

[Vincent22449268nz9k]

Thank you this worked for me!!!

[Robert Coldwell]

I am now having what seems to be a similar problem on Macos 10.14.6 Mojave with the latest Acrobat DC version. I had been combining hundreds of TIF files each week with no problem then suddenly last week I would get errors trying to combine more than about 10 images. The trick of first creating multiple PDFs with fewer images and then combining the PDFs together works fine, but that's a ridiculous workaround. The issue cannot lie with the file naming or path because I've been using the same folder for my scanner for months and have hundreds of successful PDFs created from that location. I moved files, changed filenames, filepath names, etc. with no luck. The point at which the files start showing errors changes as I rerun the combine function so it is not an issue with the files. 

Adobe, did you make updates to Acrobat for it to function on Catalina that broke it on Mojave?

[ivopivo420]

I've been having a similar problem now for several weeks, both on Mojave and latest build of Catalina. The issue arises when combining multiple image files (JPEG, PNG, TIFF all the same) into a PDF. So for example when I try to combine 50 files it will reject anywhere between 30 and 40 files with the "error during processing (file skipped)" error message. I tried different locations (external and internal SSD) and formats, nothing seems to work. This is extremely frustrating - I am forced to use native macOS procedures for the creation of PDF files, and there is no option to create a PDF file larger than A4 (or legal) size, which means hi-res original photos end up being resized dramatically. If anyone has a fix for this please let me know.

[Jay Laud]

Same issue as everyone else. Just upgraded my OS to Mohave, attempting to make a 10 page PDF of small locally stored .png screenshots which worked perfectly in the older OS, now I consistently get the same error message. No explanation or resolution of this issue. What the heck!

[Robert Coldwell]

After working with Adobe technical support on this they entered bug ADC-4287003 for this problem. I confirmed it is not the files because it happens at different points in a set of files being combined depending on whether they are TIF, JPG or PNG. It is also not the macOS version since it happened to me on both Mojave and Catalina. The latest Acrobat DC for Windows does not have this problem (and disappointingly completes the combine much faster than the Mac version of Acrobat DC - running on the same Mac hardware in a VirtualBox machine). Adobe did not tell me when to expect this bug to be fixed.

[ivopivo420]

For those who can't wait for an update: an Adobe customer support rep suggested a workaround that doesn't solve the problem in and of itself and requires an extra step. Basically, you need to create individual PDF files of the images with the "Create PDF" tool in a first step, and then proceed to merge those individual files into a single file in a second step. Like I said, this is not a perfect or permanent solution and is slightly more time consuming, but I'm glad this option is available for the time being. Thought I'd share this with those of you who weren't fully aware of this possibility (as I was). Certainly looking forward to that update though!

[Robert Coldwell]

They suggested that to me too although I already knew that was a workaround before I contacted them. For me I'm combining 1000's of page scans into individual 30-40 page PDF files so no way I'm going to double my work time like this. The problem is it seems there is a cache or aggregated file size issue so the point at which the combine process errors changes. For one set of 40 images it stopped at 16 then for another set of 40 images it stopped at 19. Trying to guess what grouping of files will work is a waste of time. Adobe rep working live on my computer spent 30 minutes trying to do just this which was frustrating. Acrobat DC on VirtualBox Windows 10 is the only reasonable solution for me right now.

[Jay Laud]

I just downloaded the legacy 2017 edition and it works fine.

[billbo65]

I have had the same issue.  Able to combine MS Excel files and Adobe Acrobat Pro 2017 PDF files, then one day get the above error message.  Funny though I used to just save all my Excel files as PDFs and then combine.  That has always worked but was very time consuming.  Then wanted to save time by combining the straight Excel file with PDF's.  That's when the problem began.  Initially did a repair in Adobe's program help section and that fixed temporarily but now back to the same problem.  Our company IT group is now looking to see what the issue may be.  No fix yet though.

[mblom_blom]

We are a print shop looking for Workstation Specifications (CPU, Memory, HDD, etc.) that would allow us to combine over 10,000 seperate PDF files into one. Do you have any guidlines? 

[Pauline5E15]

I am afraid I don't seem to be able to find the answer to this. My charity pays monthly for this subscription precisely so that it can combine complex papers for board meetings into one document. I now find I cannot do that and have tried repairing, re-installing etc. and nothing works. The files it won't combine are pdfs that have been downloaded or received from external sources. I was previously able to combine but can't now. Can Adobe help or refund our subscription please? 

[try67]

What happens when you try to combine the files, exactly?

[TKMontana]

I don't know if this will help but I had 3 pdfs that it wouldn't let me combine.  I had get them all in one pdf using "combine" but when I tried to save it I would get error 15, saying it can't read the document.  This is on a Mac.  The workaround is to one one of the pdf's in "Preview", change "View" to "thumbnail" and drag the other pdf's in.  Worked like a charm.  Good luck!

[Michael259365743vvs]

When you're in the combine window select the "gear" options and choose the middle file size.

[Pablo3307757882fo · Accepted solution]

ONE QUICK EASY SOLUTION HERE, THANKS ME LATER

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