Revision C looks like revision B
A specification is re-issued with a new revision letter and a one-line description in the revision block. The description is written by the person who made the change and reflects what they remember changing. On site, the changed tolerance in section 4.3 that nobody mentioned is what causes the rework.
Documents worth comparing
- Specifications and method statements between revisions.
- Bills of quantities between the tendered version and the contract version, for changed quantities and rates.
- Drawing sheets with text: notes, dimensions and schedules. Purely graphical line-work changes are outside the scope of a text comparison.
- Contract documents and variation orders against the base contract.
Tables and quantities
A BOQ is mostly tables. A naive text diff reports every cell of every table because the extraction order differs slightly between the two PDFs. The engine on this site fingerprints tables by content, holds identical tables out of the diff, and for tables that did change reports only the cells that changed, with their page number.
Making it a document-control step
When a revision is received, compare it against the previous revision and attach the change list to the transmittal. When a revision is issued, compare it against the previous one and confirm the revision block describes everything in the change list. Both steps take a minute with the web tool and can be automated through the API from a document control system.
Try it on your own documents. Upload two versions on the homepage. Documents up to 30 pages need no account, and nothing is stored.
Industry page: PDF comparison for construction and engineering