The quality of the PDF file and the creation date are two crucial factors for usability. A file exported from AutoCAD just last year is likely to reflect the building geometry accurately. However, if you have hand-drawn blueprints created 70 years ago, there are probably mistakes in the drawings and renovations to the building. Additionally, plans with extensive redlines could also present problems.
The PDF to CAD conversions are a budget-conscious option in multiple scenarios. You will want to consider the building type and project expectations.
Before smaller projects, the owner will provide recent drawings.
For many hospital projects, good compliance with JCAHO standards offers a high level of confidence in the accuracy of drawings on file.
In large projects, architects often have been able to visit the site and have verified the drawings on hand are adequate.
The reality is once the project has started, many clients using converted drawings discover too much has changed. It equates to a significantly extended timeline and the extra expense of creating two different drawing sets. Ideally, you have plenty of time (at least six weeks) to conduct an as-built survey if it is necessary because of inaccuracies.