Moat as its typically used is to say that a business is protected by the moat, the prize being the castle/business. The residents/business are free to build and prosper, be productive in other words.
When Keller calls it a swamp, he's trying to say there's no castle to be productive in. The swamp makes it a mess, and thus hard for the business to actually maintain productivity. It is still difficult for the invaders to break in (?) but they don't need to...because it's a swamp. They should be busy making a better castle -- which is what Keller is trying to do.
Disagree with him or not, but I think that's the analogy.
My printed copy (version 1.4) is from 2001, and that's a later version, I definitely had earlier, much slimmer books.
The 1.0 PDF reference on Adobe's web-site has a Copyright of 1993 and says "First Printing, June 1993".
https://opensource.adobe.com/dc-acrobat-sdk-docs/pdfstandard...
And of course there were multiple unlicensed implementations. Famously, Apple switched from Display Postscript in Rhapsody and Mac OS X Server to Quartz and PDF in Mac OS X to remove the DPS licensing costs.
Editing the PDF just seems like the wrong place to place the edit since it is a format intended for interchange and archivation.
Layering changes on top makes total sense. Changing existing objects seems fragile. But maybe I feel that way because the format is known for being so complicated and bespoke that only Adobe's tools can edit it reliably. Just about any document format which can be converted to PDF is easier to edit, therefore it would make more sense to apply changes before conversion to PDF, if at all possible.
I agree that reading and scraping PDFs on scale is a very common operation.
I'm not an expert, but I imagine that they were created with Acrobat and it embeds some (proprietary) stuff in the PDF that only works with Acrobat. Acrobat is also the only PDF client that I'm aware of that supports signing PDF forms with certificates. There's other features in some PDFs that I've encountered that'll only work in Acrobat as well, like buttons embedded in the PDF to email the form or dropdowns in the form that don't work in other viewers.
It seems pretty swampy to me when 90% of the PDF forms I deal with can only be (fully) completed in Acrobat.
https://jasomill.at/HelloGoodbye.pdf
contains JavaScript that, per the spec, should display a pop-up alert ("Hello Acrobat <version>") when it is opened and another ("Goodbye Acrobat <version>") when it is closed.Actual behavior is inconsistent. On my Mac:
Acrobat: both alerts display
Preview, Safari: neither alert displays
Chrome, Edge, Firefox: only open alert displays