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Brenda27663925ul6y
Participant
October 21, 2025
Answered

Using Acrobat Pro 2020 to combine PNG files and get an "unidentifiable error"

  • October 21, 2025
  • 3 replies
  • 274 views

The error only occurs when combining PNGs. Converting to PDF also does not work natively within the app, although if I change the extension outside of the app it combines fine.

 

I turned off all security options I could, the app is up to date, repair does not resolve the issue, Fast Web has been turned off, and the file doesn't seems corrupt as anything PNG doesn't work while converting it into other files types do.

 

Unfortunate there is a lot of bulk files of this type that needs to be converted so changing them all individually is not a convenient option. Is there anything else for me to try?

Correct answer AnandSri

Hello!

 

++Adding to what Olivier MOUTRET has already shared, Acrobat supports inserting PNG images, but full alpha transparency isn’t preserved when you paste or insert them directly. This is because Acrobat flattens transparency during PDF rendering. If transparency is critical, you need to use workarounds rather than relying on default image insertion. See this article for more details: Transparency flattening (Acrobat Pro).

For best results, prepare the image in another Adobe app that supports transparency and then export to PDF before combining or editing in Acrobat.

 

I hope this helps.

Thanks,

Anand Sri.

3 replies

W
william_34
Participant
October 22, 2025

hey mate, I have run into that same issue before it is usually tied to how the app handles PNG compression. Try converting all PNGs to JPGs in bulk using an external tool apk  before merging it is much faster than doing them one by one. Also check if your app has a flatten transparency option that sometimes fixes conversion errors.

[Third party link removed by Adobe moderator]

O
Olivier MOUTRET
Participant
November 12, 2025

Bonjour. Le format PNG permet d'avoir une image non détérioré, ce qui n'est pas le cas du JPG. Donc, convertir du PNG n'est pas une solution.
L'utilisation de la transparent du PNG est necessaire, sinon, il serait inutile de passer l'image dans ce format.
Bisarement, les GIF sont correctement prise en charge pour la transparent.
D'autre outil intergre parfaitement le PNG avec transparent.
Je pense qu'acrobat n'a pas évolué depuis fort longtemps en matière d'importation d'image et reste toujours avec le même dysfoonctionnement. Il faut attendre une correction qui ne semble pas arriver.

Je vous conseil ;
GIF : si besoin de transparence de fond, mais perte de la quantité de couleur et de la gestion de la couche "alpha".
JPG : si besoin d'une image sans transparent de fond.

AnandSri
AnandSriCorrect answer
Legend
November 12, 2025

Hello!

 

++Adding to what Olivier MOUTRET has already shared, Acrobat supports inserting PNG images, but full alpha transparency isn’t preserved when you paste or insert them directly. This is because Acrobat flattens transparency during PDF rendering. If transparency is critical, you need to use workarounds rather than relying on default image insertion. See this article for more details: Transparency flattening (Acrobat Pro).

For best results, prepare the image in another Adobe app that supports transparency and then export to PDF before combining or editing in Acrobat.

 

I hope this helps.

Thanks,

Anand Sri.

    radzmar
    Community Expert
    radzmarCommunity Expert
    Community Expert
    October 22, 2025

    You say, changing the file extension makes it possible to combine those "PNG" files. Maybe the are not really PNGs but other image files and use a wrong file extenstion in the first place. Open a few of them in a text editor to see the raw data. They should start with ‰PNG as shown in the screenshot below. 

     

    T
    Tariq Dar
    Legend
    October 21, 2025

    Hi @Brenda27663925ul6y,

     

     

     

    Thank you for detailing everything you’ve tried — that really helps narrow it down. From what you describe, the issue seems to occur only when combining or converting PNG files into PDF within Acrobat, while other formats work fine.

     

    This behavior can sometimes occur when certain PNGs contain unsupported transparency or color profiles, or when macOS/Windows file sandboxing interferes with Acrobat’s image-handling components.

     

    Here are a few steps you can try:

     

     

    1. Batch re-save PNGs using a system tool or another app before combining:

    • On Windows, open all PNGs in Paint and re-save as PNG (or JPG).

    • On macOS, use Preview → Export → PNG.

      This refreshes the image encoding and removes transparency or metadata that might be blocking Acrobat’s processing.

     

    2. Try the Combine Files tool directly from Acrobat’s Home screen:

    • Open Acrobat → Tools → Combine Files

    • Add the PNGs and combine them into a single PDF.

    • Avoid right-click “Convert to PDF” if that’s what triggers the issue — it sometimes uses different system calls.

     

    3. Check sandbox restrictions (Windows only):

    • Go to Edit → Preferences → Security (Enhanced)

    • Temporarily uncheck Enable Protected Mode at startup

    • Restart Acrobat and try again. (If it works, re-enable protection after testing.)

     

    4. If you’re working with bulk PNGs, you can use Adobe Bridge or a simple batch converter (like ImageMagick or IrfanView) to quickly convert them into PDFs first, then combine them using Acrobat — this avoids file-level issues.

     

     

    If this persists even after re-saving the PNGs, it might be worth sharing one sample file (without sensitive info) — this helps confirm whether the image encoding is causing the conflict.



    Best regards,
    Tariq | Adobe Community Team

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