Batch find and replace text across hundreds of PDFs

Under the hood

Why content-stream find and replace is different from search-and-replace in a viewer

A PDF reader's Find dialog walks the document, highlights matches, and asks the user to retype each one. That works for one file. It does not work for two hundred. PDF Batch Editor instead opens each PDF's content stream — the sequence of text-showing operators (Tj, TJ, ', ") that put glyphs on the page — locates every match, and rewrites the operators with new strings.

The result inherits the original font, size, and color. The replacement is written into the same content stream as the original, so the file is still a valid, signable, searchable PDF when you are done. Text-fitting modes adjust the replacement string when its rendered width differs from the original — Adaptive combines font scaling and horizontal compression for the best visual fit, Preserve Width keeps the original bounding box and adjusts character spacing, Fit to Page rescales the font, and None writes at the original size and lets the layout shift.

When the file already carries a digital signature, PDF Batch Editor uses an incremental update by default: changes are appended to the file after the existing %%EOF, leaving the original revision intact. Signatures attached to pages you did not modify stay valid. Signatures attached to a page you did modify are invalidated — which is exactly what the PDF specification requires.

Pattern matching

Regex, case sensitivity, and whole-word matching

Each pair has independent regex, case-sensitivity, and whole-word toggles. The regex engine is .NET System.Text.RegularExpressions — full support for character classes, quantifiers, anchors, lookaheads, lookbehinds, and capture groups. Replacement strings reference captured groups with $1, $2, etc.

A few patterns that come up in real document sets:

Reformat US dates from MM/DD/YYYY to ISO YYYY-MM-DD
  Find:    \b(\d{2})/(\d{2})/(\d{4})\b
  Replace: $3-$1-$2

Mask all but the last four digits of an account number
  Find:    \b\d{12}(\d{4})\b
  Replace: ************$1

Update a versioned product name across an entire library
  Find:    \bAcme Suite v\d+(\.\d+)*\b
  Replace: Acme Suite 2026

Strip a draft watermark line from every page header
  Find:    ^DRAFT — do not distribute$
  Replace: (empty)

Whole-word matching uses an IsLetterOrDigit boundary check on the characters before and after the match. Searching Smith with whole-word on matches Smith, but skips Smithfield and Smithy. Case-sensitive matching is on by default; flip it off to make Acme, ACME, and acme equivalent.

Multi-replace

CSV-driven substitutions for hundreds of pairs

Annual updates are rarely one substitution. They are dates, addresses, contact names, internal codes, version strings — sometimes hundreds of pairs across a contract library. Build the change set in Excel or Google Sheets, save as CSV, and import:

find,replace
2025,2026
Q4 2025,Q1 2026
123 Old St.,500 New Ave.
"Acme Holdings","Acme Holdings, Inc."
v3.4,v3.5

Each row becomes one pair, applied in order. Pairs chain through temp files internally, so a later pair sees the result of an earlier one — useful when a substitution depends on an earlier one. Mix imported pairs with hand-edited pairs, expand any row after import to override its options individually, and export the current pair list back to CSV for version control or sharing with colleagues.

Per-pair controls

Page ranges, signatures, formatting, and conditional skipping

Each find/replace pair has its own independent settings, accessible by expanding the pair row.

Edge cases

Scanned PDFs, signed pages, encoding, and form fields

Scanned PDFs without an OCR layer. The tool reads the content stream, not rendered pixels. A flatbed scan that has not been run through OCR contains no text operators — just an image — and there is nothing to find. The preview will report zero matches and a "may be scanned/image-only" warning. Run OCR first, or replace text in the original Word/Excel source.

Signed PDFs. Incremental save (default on) preserves the prior revision, so signatures over pages you do not modify continue to verify. Signatures attached to a modified page are invalidated by design — that is the entire point of a signature. If you need to keep all signatures intact, restrict the pair's page range so it does not touch a signed page.

Custom encodings and Identity-H fonts. Most PDFs use a ToUnicode CMap that maps glyph IDs back to readable characters. PDF Batch Editor extracts text through this CMap, so well-formed PDFs work transparently. PDFs generated by older or hand-rolled tools sometimes ship without a CMap or with a broken one — in those cases the live preview's match count may under-report even though the underlying content stream still contains your search text. If a file's preview shows zero matches but you can clearly read the text on the page, the PDF likely lacks a usable text-extraction layer.

AcroForm fields. Find/Replace targets the visible page content stream. AcroForm field values live in a separate dictionary; once a form widget's appearance has been generated and embedded into the page (the usual case after a form is filled), the visible text is matched and replaced like any other content. Empty, unfilled forms are best handled by the dedicated batch form-fill module.