InDesign exporting PDF Adobe Preset vs Standard

I've always considered the pre-loaded PDF presets as 'guides' and 'starting points' for the PDF settings. 

As @Willi Adelberger points out the PDF settings can be tweaked and changed depending on specific requirements from printers. 

@Dave Creamer of IDEAS and @leo.r have covered a lot - so no need to go over them

If your designer picked PDF/X-3 in "Adobe PDF Preset" but PDF/X-4 in "Standard," InDesign will apply the Standard setting (PDF/X-4 in this case), overriding any conflicting settings from the preset. The final PDF will follow the PDF/X-4 rules.

InDesign splits the PDF export settings into two parts. The "Adobe PDF Preset" handles things like image compression, font embedding, and colour conversions basically, the technical tweaks.

The "Standard" setting, on the other hand, tells InDesign which PDF compliance (like PDF/X-3 or PDF/X-4) to use for the final file.

PDF/X-3 flattens transparency, while PDF/X-4 keeps it live. So, a designer might choose a preset they’re comfortable with (even if it’s set for PDF/X-3 parameters) but then set the Standard to PDF/X-4 to benefit from live transparency if the printer’s workflow supports it. In the end, the Standard setting takes precedence, meaning final file will be PDF/X-4.

There can also be a bit of habit or even a misunderstanding involved. But if the printer needs PDF/X-4 (for its ability to maintain transparency), that’s the setting that really matters at export.

The presets are a combination for all settings which makes it easier to  create PDFs. I create for each printer and purpose a different PDF presets.

When you import/place PDFs to InDesign it schould always be PDF/X-4.

When you export PDFs for a printer you should do it according the requirements of that printer. Save for each printer and product and ppurpose a specific preset as helps to avoid errors.

The Preset setting is just a name that has saved settings for General, Compression, Marks and Bleed, Output, and Advanced--plus it switches to the matching Standard if it has one.

The Standard makes sure the requirements of the standard are met. For example, choose a preset of PDF/X-4 when allows any color (RGB, LAB, CMYK, Grayscale) and transparency. Then change the Standard to PDF/X-1a--the color will change to convert to destination since 1a only allows CMYK and grayscale; the transpareny will change to high resolution flattener since 1a does not allow transparency.  Generally, PDF/X does not care about resolution or crop marks/bleeds.