I have trouble with Acrobat trying to flatten some PDF files.

Here’s the situation.

Our printer requires PDF files without transparency so in most cases I export a PDF/X1-a directly from InDesign.

But for some documents I have to do some extra steps. These documents contain technical drawings in PDF. Because of scaling some lines are too thin for print.

I don’t want to edit the PDF of every single image to solve this what would take a lof of work and many different versions of the same drawing. Therefor I apply a hairline fix in Acrobat to the final PDF of the document (all hairlines to 0,25 pt). This also makes drawings at different scales look the same.

However, many of the drawings contain transparency. When exporting a PDF/X1-a (= flattened PDF) from InDesign, some strokes are converted to raster image or outlines (even with raster-vector balance set to 100 and ‘Convert all strokes to outlines’ turned off in the transparency flattener settings). Because of that, Acrobat can’t fix these hairlines anymore.

So my solution is to flatten the PDF after the hairline fix:

Step 1: Export the file as PDF/X-4 (keeping transparency)

Step 2: Apply a hairline fix in Acrobat (all hairlines to 0,25 pt)

Step 3: Flatten the PDF using Acrobat.

The problem:

On some files Acrobat crashes on step 3. I see the progress bar going to 100% and then Acrobat crashes without any error.

1. BUT... if I skip step 2 (the hairline fix), then Acrobat finishes step 3 without problems. So there must be something with the hairline fix that causes the transparency flattener to crash.

Here are example files:

• Example WITH hairline fix
  
• Example WITHOUT hairline fix

Using Acrobat Pro DC 2017.012.20098 on Mac.

All help is appreciated!